I swear I just answered this yesterday but it's AAKK double suited.
Also, it's important to understand that even the best hand in Omaha is rather vulnerable compared with AA in Hold'em. AA in Hold'em is an 85% favorite over a random hand, while AAKK double suited is only a 71% favorite over a random hand in Omaha.
This is part of the reason why winrates are comparatively lower in Omaha and the rake is a bigger obstacle.
Read this Thread https://www.cardschat.com/forum/learning-poker-57/omaha-poker-only-luck-play-skill-273460/If aces is the best hand in texas holdem then what is the best hand in omaha?