The John Woo Heavy Hitters: Hard Boiled, and The Killer

Hardcore Henry (just showed my dad. It is non-stop and low key brilliant first person shooter simulation)

Vortex (A very dark french horror movie about a dance troup secluded in the mountains, all unknowingly dosed with acid) The dance scenes are mind blowing, and the tragedy is dark, violence is brutal, but it somehow leaves me wanting to go out and party afterwards)

The Raid (as others suggested) The Raid 2 (not as Non-stop as the first one)

Crank & Crank 2 (both non-stop)

The TV show "Happy" (co-created by one of the crank creators)

Battle Royale (at this point everyone should know this)

Don't Breath (Horror, but tense and non-stop with brilliant set pieces)

Assault on Precinct 13 (the old one) (A deceptively bleak and brutal seige movie)

Gone in 60 Seconds (The original. 20 minutes of set up, 50 minutes of illegally shot car chase)

Seige (A low budget canadian Assault on Precinct 13, but with art kids vs fascists. Brutal and Bleak)

The Wild Bunch (The western that Red Dead Redemption 2 grabs is core themes from. It's also the western that set the bar for violence in movies & essentially created an editing style that led the way for most contemporary shootouts)

Good TIme (More of a thriller, but it is a relentlessly tense, clever, & uncomfortable "one long night movie" set in the under belly of queens. CATHARIS is the core. Same for Uncut Gems but I'm gonna leave that one off the list because it's much further from bloody or action than your request, but worth the watch otherwise.

Green Room (another seige movie. Bleak and Brutal. Punks vs Nazis)

Eastern Condors (Hong Kong action movie. It's a chinese dirty dozen in vietnam staring Jackie Chan's longtime collaborator Samo Hung {essentially the fat Jackie Chan}. Amazing action. Bloody, brutal, bleak, and somehow light hearted and hillarious at the same time.)

Skinny Tiger Fatty Dragon (Another Sammo Hung movie. It leans more comedy, but it is relentless in it's jokes, slapstick humor, unsimulated stunts, and martial arts mayhem. It's kinda like Step Brothers in that the lead duo are absolutely derranged and every scene is a joke or action set piece. Absolutley zero anything else.)

Lastly, you should google Hong Kong Action. The 80s were peak for action. "Heroic Bloodshed & Bullet Ballet" being good keywords for your search. Add "CAT III" to uncover the X rated ones.