get better than him at judo.
Why not just use subterfuge - bribe the officials, or better yet the bracket makers to get away from that dude, or just switch divisions? Or become head ref and change all the rules. If you make up your own tournament with your own rules you can be world champion.
Of course that takes money and imagination, plus internet access so you can spout off about your ability, so maybe it's better to just lose and blame the refs, blame the rules, blame the bracket...
1) Kick him in the nuts
2) Fight him after he couldn't train for a month, due to a neck injury.
3) Change the rules so theres No way he can get a decsion win.
4) Change the rules so if its a draw "you" win.
5) By chance if the judoka "actually" wins, say he didn't use judo to win, and must train bjj.
Chop his arms off and his legs and his nose and his Elvis. Then pass his guard. It's as easy as one, two, three.