Zampano

Zampano is an all rounder neutral with decent tanking, damage, and stuns. He is primarily defined by his ability to scale his stats infinitely with his W, having by far the greatest scaling potential of any hero in the game. Without upgrades, his best ability is generally his stuns.

Abilities
D - Ranged Assault: Zampano fires spikes from his back as his primary form of attack for 15 seconds, giving him 800 range and decreasing his attack cooldown from 2.2 seconds to 1.8 seconds. 45 second cooldown.

F - Spiked Back: Zampano's spiked back gives him 20 bonus armor and the ability to return 30% of melee attack damage to enemies.

Q - Spike Spray: Zampano fires spikes against all those around him, dealing 200/275/350/425/500 damage to all enemies within 625 range and stunning them for 1/1/1/1.25/1.5 seconds. 23 second cooldown.

W - Voracious Pig: Zampano bites the target unit, dealing 300/375/450/525/600 damage to them, stunning them for half a second, and healing himself for half the damage dealt. If this kills the target, Zampano will gain 1/2/3/4/5 max HP if the target was a unit, and 1/2/3/4/5 Strength if the target was a hero. 23 second cooldown. E - Spike Rain: Zampano fires 30 spikes from his back at the target point, each spike dealing 9/11/13/15/17 damage for a total of 300/360/430/495/560 damage if all spikes hit. The spikes stun enemies for 1/1.25/1.5/1.75/2 seconds. 300 area of effect, 700 cast range, 32 second cooldown. R - Boar Impale: Zampano extends his spikes from his back, dealing 600/725/850 damage to all enemies in front of him within 250 range. 40 second cooldown.
 * The bonus HP/Strength is increased by 1 per upgrade. This retroactively applies to HP/Strength Zampano has got from previous uses of W.
 * The healing is a set amount. If the damage dealt to the target is reduced, such as by hitting Envy in his ultimate, Zampano will still heal the normal amount he would by using the move on a target with no damage resistance.
 * Neutral/NPC hero deaths will still give Zampano bonus strength.
 * Homunculus stone charges being taken will give Zampano bonus strength.
 * Triggering Slicer's ultimate/Father's reincarnation also gives bonus strength.
 * This is a channeled spell that takes roughly a second to complete.
 * This ability's cooldown is reduced by 2.5 seconds per upgrade.

Playing as Zampano
Zampano is entirely defined by his simplistic W, Voracious Pig. You never want to stop eating with this ability, ever. Gluttony does not eat even half as much as Zampano over the course of the game. The cooldown is low enough it can reasonably be spammed for excessive HP, even when you're level 35 already. It may not seem like much using W on units, but the extra health will add up over time, especially if you're remaining neutral. Just make sure to not waste the ability when a hero you could potentially eat might be nearby.

W is your bread and butter. Not only do you use it to scale, but it is also your primary DPS ability if you're using upgrades. If you are not neutral or don't have upgrades yet, the damage on it is not very high, so you will want to use it exclusively for scaling in those cases. To play Zampano optimally, obviously you want every single kill to end in a W if it is at all realistic. It is generally easier to use R as your finisher if you are strictly concerned with getting the kill, as R is the hardest ability in your kit to hit due to the low range on it and it not having a stun. However, you must resist the temptation to finish with R, and use it before W if at all possible. The strength is just too worth it.

Much like Pride, Zampano really wants all kill credit to specifically go to him and his W if at all possible. If you need to really push your point to your allies, offer to give them gold/items from the kill if needed. Competent allies should give Zampano kills whenever possible (unless they're Pride, who should take priority over Zampano). It is not always realistic for Zampano to get the kills over his allies due to him being a slow moving hero with slow abilities and only a couple longer range ones, but in the case of bosses, Zampano's allies have no excuse to not give him kill credit. NPC bosses generally have bad copies for Pride anyway in most cases, unless they're a playable boss like Greed or something. Make sure you get every boss kill that you can. Zampano also has increased motivation to go for Cray/Buccaneer for the potential strength gain, though he should avoid Doctor/Winry unless he wants to just end the game. If the Homunculus team has no doctor heroes, though, the doctor is free to eat with W.

Zampano is an inherently homunculus favored neutral. He wants to hunt down as many low health heroes as possible and kill them as much as he can to get that delicious bonus strength. If the enemy team has Kimblee, Tucker, or Cornello, you can try to kill them also. You want to find some enemy players who are particularly bad who you can feed off of over and over. This can apply to any Hero, but it applies moreso to Zampano. As far as finding a random hero to kill, an alchemist will almost always be easier. If you can manage to hardcore bully a character to low levels, though, a doctor character can be a better target, since their allies are less likely to punish you for it.

For his utterly ridiculous potential stats when he gets upgrades, Zampano still has no realistic hope of winning on promised day in most games. General neutral rules apply here - wait on the left side of Central, team up with Alchemists, and betray them at the last second. Zampano will generally need to be allied with a Greed Gang character and use their secretary to heal to have any hope of surviving Promised Day. His health will do nothing against the pentagram, and he should exclusively let alchemists deal with Father Form 2.

Zampano's other abilities are very simple to use and nothing complicated. Q and E are your ranged stunners and openers. E is a channel, so it is usually better to open with Q than E if you are chasing someone. R is your hardest ability to hit, so just use it whenever you get a chance at close range and it won't kill the enemy. R gets a very low cooldown with upgrades, so remember to spam it whenver in close range.

Zampano's spiked back passive has minimal impact early in the game, but is much more useful if he has scaled extensively with tons of HP to reflect damage with. Autoattack heroes will be hurt very badly by this ability, such as Wrath during his R. The W of Edward is also entirely autoattack damage, so it will reflect a lot of damage back onto him.

D is not an especially useful ability unless a couple extra autoattacks will get you a kill it wouldn't otherwise. Zampano wants to be in close range to use his W, which is what he revolves around. W should primarily just be used for the increased attack speed more than the range.

Playing against Zampano
It goes without saying, but don't feed Zampano. If you let him get a foot in the door, he'll become a nightmare. If he becomes strong enough on the neutral team, the only real answer to him is to backdoor his house. Homunculi will rarely have this luxury available to them unless they have Wrath on their team, whereas Alchemists can go after the house with the plethora of invisibility characters at their disposal. Zampano is one of the biggest potential characters to carry a neutral team, and is someone you should take seriously. He is also a very useful hero even if his stats are taken from him by being revived onto a team, so feel free to just end his reign of terror early and destroy his house.

If you are for some reason dealing with a Zampano with ridiculous stats due to some noobs feeding him, you want to use any % based damage abilities against him you have. The only ability in the game that directly does this is Kimblee's F, which can do massive damage to Zampano. Aside from that, you're mostly just looking at the pentagram. If desperate, Gluttony can eat Zampano and carry him into the promised day, since he only needs to be killed once. This is obviously very risky, so you're probably better off hooking and eating his secretary in that scenario, so that he can stop running and healing.

One of the biggest sources of stats Zampano will get that can start to get his infinite strength scaling rolling is those from bosses. Simply contesting bosses and preventing him from getting them can be a big detriment to him. Assuming he gets his 10 upgrades eventually, he will get 15 strength, which is almost comparable to the 25 strength Scar gets from a state alchemist kill. Unlike Scar, Zampano can do this to every single boss, which is generally speaking a better deal. It's not like Zampano is going to miss the 25 agility Scar gets all that much anyway. Make sure you contest bosses! If you're looking to kill him to keep him underleveled, Zampano is almost undoubtedly going to be showing up to every single boss spawn anyway.

Trivia

 * The only other Hero besides Zampano able to theoretically attain infinite Strength is Sloth with use of Break Time, but even if Sloth did nothing for the entire game, the maximum amount of time a game can go before Homunculi automatically win is 70 minutes, meaning he can only get a max theoretical strength gain of 100 strength. Zampano can get well over 100 bonus strength, getting up to 15 strength per hero kill with 10 upgrades. Even with no upgrades and joining a team, getting 5 bonus strength per kill isn't a bad deal.
 * Zampano's sin priority when becoming a homunculus is Gluttony > Sloth > Pride > Wrath > Greed > Envy > Lust.