I think poor Set gets a bad press. He just had a bit of a temper and was full of pride. After all Osiris was his younger brother and yet Osiris was made Pharaoh instead of him. That must have been really annoying. Then (according to some myths) Set's wife seduced Osiris, and that can't have helped.
In earlier myths which place Set in opposition to Horus, he isn't depicted as particularly nasty. Instead he represents Upper Egypt while Horus represents Lower Egypt. Some think that the followers of Horus won the battle to unify Egypt ans started to depict Set as a negative influence. He was also associated with the Hyksos invaders who seemed to like him for his warlike nature. But Ramessess II also appreciated his martial skills.
It is time to rehabilitate this missunderstood god and stop calling him evil.
I think the most evil entity in Egyptian mythology is Apep (Apophis) the serpent that tried to devour the sun every night. Set was one of the deities who protected Ra from this dangerous being, but it seems he fell out of favour with the sun god because he was so boastful and proud.