4. Spider
This to me seems to be an addition from the original version of the game. One of the major problems with it is that it is just too prevalent! If it didn't appear as much, or if the game treated it as an actually difficult enemy (which it is!), then it would be more OK. But alas it is treated as the completely harmless static fly, and the game just POURS these suckers on you. Many bosses spit these out at you, worst of all is of course the big flying ball which splits up into smaller balls and and puke these SoB's at your sorry ass.
The main problem with the spider is that once you get close enough to it, it will decide to lock on to you, and once it starts moving it will move very quickly towards your destination. It will easily round corners as well while doing this. The problem is you as the player has no idea when you are close enough for it to lock on. Because if you are not it will just randomly move in a given direction. A simple solution would have been to just make it flash a different color when locking on. Just imagine the spider never stopping, and always locking on to you. It would be the worst enemy in the game. It would not be acceptable, but the problem is, once you are close to it, and if you don't react correctly and/or your speed stat is not high enough, the spider virtually *is* that enemy, albeit for a very short time. I call the spider bosses, because they are much harder to avoid taking damage from than most bosses, couple that with how often they appear and that's a very bad thing.
3. Bony
Once your speed stat, and of course, the damage stat, is high enough, these pose less of a problem. But they are still fundamentally annoying. Once you step into one of these guy's cardinal directions, they will very quickly stop and shoot a very quick bone shot, towards your *current* location - meaning they can throw them diagonally! And if you would happen to stay in the cardinal direction, they will continue to throw bones for all eternity in very quick succession (this one blows my mind how you can come up with at all)! So yeah. How do you shoot an enemy in this game again? YOU HAVE TO BE IN THIS FUCKING THING'S CARDINAL DIRECTION! Meaning you have to swipe past it quickly and time your shot so that it hits, while dodging the bone. The main problem is that the bone is so goddamn fast, it gets shot directly at your position, and Bony does it so quickly in succession. It's just poor design, through and through, the definition of artifical difficulty.
2. Leaper
Oh God help me from this thing. It's just a brain fart all the way through. Once it jumps its small shadow is often very difficult to spot, and then it more or less teleports onto your position and shoots out very fast bullets in its cardinal directions. It's always so nice with enemies that teleport directly onto your position. That is the definition of fun. You can't even shoot it directly since it fires in all four directions, and then often will just jump away again. To add insult to injury you often meet four or more of these at once.
1. Drowned Charger
Noooooooooooooooooooooooooooooooooooooo!!!! Do not want! Why, oh why did you add this enemy with the fucking DLC???? It has SO much health, charges towards you, and it by design rewards poor gameplay! If you try to dodge it and it dies, you almost always get hit by the diagonal bullets it shoots out as it dies. So you have to stick to your guns and play a kind of "chicken race" with it, hoping you will kill it before it charges into you. How can you even come up with something like that? It's like penalizing the player in Super Mario Bros for trying to jump on a Goomba! I'm out.