Only three things matter: health, armour and ammo.
… and killing the screaming suicide bombers before they get to you.
Serious Sam 3 is 80% off on Steam at the moment.
It’s a good old fashioned shooter with great guns and hordes of enemies to splatter. Think a modernised mix of Doom or Quake alongside Duke Nukem 3D (the good old one, not the shit new one). No pretensions or complications, moral choices or strategy: just blow up the bad guy aliens before they splatter you all over the walls.