I reckon his biggest achievement, though it wasn't his alone obviously, was the Brexit deal, where he, and the European side generally, showed much better grasp of technical detail than Johnson and his clubby buddies.Could it be said that Leo's finest moments were during Covid.
It could also in my opinion have given him a false sense of infallibility when he was able to impose any restrictions he saw fit.
He deviated from Nphet advice also which wasn't a good look.