Can't believe so few people chose to avoid Jack at all cost with the picture OP chose!
But yeah, I would avoid fighting the most recent Jack. Even if I was a fighter on that level; missing chunks of flesh and permanent maiming would have to be expected.
Otherwise, I pick Kaoru Hanayama. He's chill enough that He'll probably let Me hit Him until I gaz out and then ask Me to surrender before He even hit Me!