Genetic Disaster (EP)

The final boss of this game is luckily not that hard if you're playing on easy. Let's go over his different phases, then I'll explain the best way to take him out.

Missing Link, a monkey scientist, is the only boss with three phases. He shows up on the 12th floor and starts off with a run-and-gun section. You'll be chased by a poisonous cloud while boxes and crawlers are in your way. Every now and then, ML will show up behind you to throw a bomb.

The second phase, as well as the third...
Well, this is rather awkward actually. I've never really gotten to fully experience ML in these phases, because I usually kill him incredibly quickly. Much of this is due to the "Eradicator", weapon, a very rare purple-tier weapon I've luckily gotten the two times I've fought him. Note that there are two versions of this gun, the best one being the gun with stripes on its barrel. If you can get this gun, you NEED to get it, it's ridiculously powerful.

However, this should still not be that hard if you can survive the first chase. Get yourself a high-damage weapon, play as Devil and just burst him down quickly. It should be a piece of cake.