Adonis is a character that is simple, yet still terrifying. He has a battlesuit that gives him incredible strength and durability, to the point that attacks Cyborg and Starfire (two of the strongest Titans) don't even affect him at all. It took a feral Beast Boy to claw him out of the suit.
What's worse, chemicals turned him into a werebeast of sorts, and it led to him going after Raven. Only a similarly transformed Beast Boy was able to defeat him.