I'm going to say Savage Worlds. Technically, the most enjoyable combat for combat's sake I've had was D&D4e, but I don't play that anymore.

Here's the thing, different people want different things from combat, so a lot of it isn't whether a game is good or bad at combat, it's whether it does combat the way that person likes it.

Savage Worlds has great combat. It's very crunchy, very tactical, expects you to use miniatures (and benefits from doing so). If that's what you want from combat, you are unlikely to find a much better system. If that is not what you want, it's probably close to the worst for you.

Compared to other crunchy tactical miniatures combat, it moves very quickly, has great options for non-combat focused characters, and is very easy to run/manage from the GM side.

Flat out, there is no other RPG that does all that.

There's plenty of games that are faster and easier, but they don't have the same crunchy tactical miniatures combat.

There are games that have better crunchy tactical miniatures combat, but they aren't as fast, or as easy to run, and don't have good options for non-combat focused characters.