Lex has the capability to be a physical threat inasmuch as he can create things like the mech suit to fight Superman, heck he has even been Superman for a while in early Rebirth runs. But Lex is most interesting as a master manipulator. He’s a walking contradiction inasmuch as he is untrusting of Superman as an alien, but he is willing to compromise and to tap into any number of extra terrestrial or supernatural powers to try to bring Superman down.
If there is any Marvel character that I would relate Lex to, it would be Loki because Lex can be very sympathetic and charismatic. He is often dancing on the line of hero and villain. And when he is full on in hero mode, he is effective and you as the audience don’t know whether to cheer him or not because you don’t know what his endgames are and whether you are being played or not. Superman and other characters are in the same boat.
Lex is also the perfect foil for Superman because in many ways he brings out the best in him. I love that Mark Waid has written that Clark’s greatest desire is to see Lex reformed and to be reconciled with him, but he knows that he cannot trust him.