A complete lack of blood and gore, in any meaningful way.
Take Fallout 1 & 2. Even on zoomed out poorly scaled resolutions, you can see how every gun has a chance for a unique death animation to take place. The SMG will shred the upper right half of the body, and some guns give a chance of blowing out your lower torso, and give a cry of fear and regret before slumping down. A rocket launcher is more boring but subtle cool in how it just has an explosion, then disappears the whole body, and if I recall sometimes you can only see the feet there. There was that one super mutant in the Mariposa military base, who just had the most surreal, unique death animation out of all the enemies in the game. I don't remember it quite well, but I recall squinting my eyes in this fascinated wonder that only can be described as like when you witness a car accident and can't stop staring. Had this Berenstein effect the other day where I swore I saw that enemy in particular rip in half and crawl towards the player chara, but when I looked at it on youtube it was something else.
On that same note, appropriate death sounds for the right deaths.
It can add a lot of character to combat based games, while also adding to story based games. Too often I see developers implementing this wild ways to take down enemies, "Look how the player can sneak up behind an enemy, slip their machete out from their holster, and proceed to slash said enemy's leg off before beating the absolute living shit out of him." But the "Beating the absolute living shit out of him" part is more like a single or two swings before the enemy defaults to a family guy pose onto the ground that may or may not have blood.
It actually bothers me when there isn't enough meaningful blood and gore in a game. I'm not talking gigantic oceans of red here, I'm talking "Did I fuck him up? How do I know?" and Underrail is guilty for having this stiff nature to getting shot that just floats up a number and that's it. That being said, the animation that plays when someone's lit on fire - it's like night and day, and I love that one.