How do you deal with an extremely uncooperative shard member?

Nah, don't let him win. It's a competitive game mode yes, but hitting people all hours of the day to stay top 2 isn't competition it's just being a **bleep**. There's no rewards for the other 23 hours he's there. So tell your shard to keep hitting him every time they can. If you have a discord and people are spread out, you can coordinate to have someone else drop him as soon as someone else knocks him down. That, or have someone  start a battle with you about 6-7 minutes till your payout and let the timer run out to lock yourself. Or you can start the battle.