The only thing close to it that happened was Lex getting cancer from Kryptonite exposure in the 1990s.
He created a clone (Lex Luthor II) and had his brain transferred into that body.
Smallville's Lex actually died in the truck explosion.
The new Lex from the finale is a combination of the best parts of the Lex clones. Franken-Lex.
I would have preferred Lex to have stayed alive till Season 9 at least, and have Zod kill him off. The Oliver murder thing went nowhere.