Here's why it's hard to say definitively which enemy he *didn't* bite:
* He's bitten a lot of enemies. He bit Vegeta, Frieza, and even Cell in different battles.
* It's not a common tactic. Biting is more of a desperate move than a go-to strategy for Goku.
* We don't see every fight. There are countless battles off-screen, and it's impossible to know if Goku bit an enemy we never saw.
So, the answer is that there are likely many enemies Goku didn't bite. It's more about which enemies he *did* bite, and why those moments were memorable.