Some have reported getting one hit kills on them from bandits. Has not happened to me except when I stand there and take a power attack without blocking or dodging, and that is rare to come across this enemy.
I am at level 41/42 and I find enemies that are much weaker than me, most that are near the same level as me, and I find some that are tougher than me. However, you will find enemies that are tougher than you at most lower levels as the game is made that way. In other words, stay out of the mountains until you are ready. If you play the game and don't grind to create an super character or one that can create great weapons but has no skills to use them, then you will find the enemies are about what they should be: Most are handled by your characters, some are a challenge, a couple will make you want to come back later when you are ready.
There are a number of posts that I've seen recently that state if you power level enchanting, smithing, alchemy, your character will increase in level, but it's combat capability will not. So, you may go back into the dungeons where enemies are your level, but their combat capability is higher than yours, and you can/will be one-shot.
Is this correct? Or not.
I would think that with many different players saying this, there must be something to it.