Honestly? Nobody has true ponkotsu immunity. Even the "perfect" ones slip up eventually.

Suisei comes closest - girl's scary competent at almost everything. But she's had her moments too.

Maybe Botan? She's got that cool older sister energy and actually seems to have her life together. Though being too perfect is sus in itself...

The real answer is that ponkotsu energy finds a way. It's like entropy - inevitable and universal in Hololive.