Any boomer shooter should do the trick, like all of the doom games, dusk, turbo overkill, ultrakill, etc. Their difficulty is flexible too so you can have a challenge or just a vibe with killing whatever is in front of you. Most of these games have an endless mode that works perfectly for small sessions. There's TF2 if you're in a mood for quick online games.
Any boomer shooter should do the trick, like all of the doom games, dusk, turbo overkill, ultrakill, etc. Their difficulty is flexible too so you can have a challenge or just a vibe with killing whatever is in front of you. Most of these games have an endless mode that works perfectly for small sessions. There's TF2 if you're in a mood for quick online games.