Green’s Dictionary of Slang

whipass n.

also whoop-ass, whup-ass

1. (US) energy, determination, aggression; also attrib.

[US]D. Jenkins Life Its Ownself (1985) 15: I, me [...] your basic, all-pro immortal, was expected to go out there every Saturday and crack open a 220-pound can of whipass.
[US]F.X. Toole Pound for Pound 56: ’Bout time t’open up a can a whip-ass. [Ibid.] 121: This Chicky-dickie a whup-ass Messkin boy who will fight.

2. a beating.

[US]Simon & Burns ‘Boys of Summer’ Wire ser. 4 ep. 1 [TV script] Give ’em a whip-ass they aint never gonna forget.

In phrases

open a can of whoop-ass (on) (v.)

to assault, to beat up.

[US]College Sl. Research Project (Cal. State Poly. Uni., Pomona) [Internet] Bust open a can of whoopass (phrase) To prepare to beat someone up/get really angry after they’ve done something appalling. (Usually meant as a joke between friends.).
[US]Source Oct. 120: He even opens a can of whoop-ass on a bigoted cop.
[US]Teen Lingo: The Source for Youth Ministry [Internet] open up a can v. (derived from ‘open up a can of whoop-a_ _’) To take an action of enforcement. To punish or hurt.
[US]Mad mag. Dec. 9: I’m going back to Mustafar to open a molten hot can of whoop-ass.
[US]Simon & Burns ‘Combat Jack’ Generation Kill ep. 4 [TV script] At oh-dawn-hundred tomorrow the Navy’s launching some precision-guided whup-ass.
Twitter 2 Aug. [Internet] Watch Journalist, Dr. Sarah Kendzior, Open A Can Of Whup-Ass On A Breitbart Editor!!!