Some enemies are annoying.

[Rock&StoneTorture]

Red slime and that green slime who one shots you are annoying as ♥♥♥♥... Lost most of my loot because of that green slime ♥♥♥♥♥♥... There is not even a warning that it could one shot you...

[XistenZ]

I can't remember if the "green slime" (I assume you're talking about the wanderer) is mentioned by possibly Petes notes or someone in town. Either way it should be made clear that it appears when you've been idling around or just take too long in the dungeon as a timer icon appears on screen before he pops up. First time facing off with this dude one probably tries to attack it, which teaches you the lesson that it's invulnerable and one-shots you.

If he appears all the time you need to get more effective at dungeoneering. He should only be able to kill you once, possibly twice if you think you messed up the first time. If you can't runt away from it then just portal out, it's better than loosing everything since by the time it comes for you you probably have your inventory full to the brim with loot.

[[BLK] Telu]

Yeah, main goal is to learn how to deal with enemies.

For slim, you need to dodge roll to them, that's force them to fail their attack and allow you to strike them.

For the big green slim, yes, it's annoying, you have just enough time to explore a level completely. You can't take your time to play. I don't like that also.