Be it in general or a given enemy, using an exploit or gimmick, it doesn't matter. After all...This IS the cheats forum.
It would be interesting to see where your imaginations take you.
I was able to take out Umbra, at level 1. I play with the diff set at 100, so I need all the help I can get. Umbra is one of the toughest enemies you will find. She is a level 50 baddie, no matter the level you encounter her. I used the 'paintbrush drop' to do it. I blocked the door, at the top of the stairs from her with about 10 paintbrushes. Each one dropped about 6 inches apart and around waist high. I stood on the balcony and hit her with a fireball. Here she come. She ran through the makeshift blockade and struck me once. With a sliver of life left, I jumped down to the lower level, and ran to the opposite corner. Healing all the way. I waited for a few seconds...She never showed up. I had the Apotheosis staff ready. I slowly made it back up the steps, and there she was. Running in place. Stuck behind the paintbrushes. It was like shooting fish in a bucket, at that point.
Granted that, THAT staff would have probably taken her out with a bit of running around and backpedaling. ( the usual strategy ) The paintbrush trick worked out ok.