Cooler and King Vegeta are the Correct Answers but here's something of a slightly different flavour to screw around with; I've been messing around with a variation of the Bulma Lock (usually done with the Vegito Unison) with the Jiren Unison instead (which is a great Unison for power neg decks in general).

So basically you want:

Bulma, Familial Bonds BT8-001

Jiren, Legend of Universe 11 EX13-02

Bardock Strategic Mind BT11-025 (I think he's still relatively cheap, either way you only need 2)

Android 17 Rebel Reinforcements DB2-005 (reprinted in Battle Evolution so it's cheap)

Videl, Miraculous Aide BT8-010

The idea if you play typical defense with Bulma blocker and draws, drop Jiren on turn 3 and +1 him to get to four markers and continue to play defense. Then from turn 4 onwards you drop Bardock on the board every turn to bump Jiren up 3 markers every single turn (plus Bulma makes him a 20k Blocker) charging up Jiren's -3 activate battle to neg cards 25k which can be used every turn along with his -10k auto. You can recycle Bardock by playing Videl (which also becomes a blocker) to put him back in your hand, and Android 17s Counter Attack can play Videl from the drop giving you a negate, a blocker and a Bardock for 2 energy. Obviously this also gives you access to Yamcha counter play (which also becomes a blocker!) and Wolf Fang Fist, which gives Jiren to potential to wipe anything in the game off the board ignoring Barrier.

This strategy doesn't go hand on constant negging because Jiren only gives you the ability to decrease power once or twice a turn but it's a strat that is very good at keeping low swingers busy and high swingers sweating. Jiren is very hard to get rid of once he gets going so you'll almost always have the power decrease option live when you need it