If you want a little more hesitance about violence, IME emphasizing the gore won't do it. What you have to do is emphasize the human cost, the social connections and consequences. E.g., in a cyberpunk game once, the PCs had just hacked to death a drug dealer, a few seconds after he shot a street kid for trying to pickpocket him. They do the usual "loot the body" - and in his wallet alongside losts of cash, they find pictures of his girlfriend, a list of phone numbers including ones for "Mom" and "Dad", and two tickets to the rock concert tomorrow night, by the same band one of the PCs is a big fan of. That brought the players up short a little. For just a moment, he wasn't a faceless mook, but a guy with parents, a lover, and at least some interests that matched their own... They still took the loot and skedaddled, but there wasn't nearly as much crowing about the kill.
As to detail in violence, a lot depends on the group. I tend to avoid it in convention games, both because of the tight time limit and because I've found the most frequent reaction is one of two things: either it creeps the players out and they start looking at me funny and backing away... or they revel in it ("Yeah! I rip the guts out of his bleeding corpse and throw them in the face of the next guy!"), which causes *me* to look at *them* funny and start backing away...
With our usual group, it largely depends on the importance of the opponent. More important opponent, the more descriptive the death. E.g., a PC has just dropped a female wolfen (like gnolls, but wolf- rather than hyena-based) to negative HP with a sword blow:
Nameless mook:
"You hack the wolfen in the neck. She gurgles and collapses."
Minor named NPC:
"You slash the wolfen's throat from ear to ear. She drops her spear, clutches her neck, and falls to the ground, where she gurgles and thrashes in her death throes."
Major NPC:
"Dodging the wolfen's spear thrust, you lunge forwad and slice open her throat from ear to ear. Dropping her spear, she coughs and clutches at her throat with both hands, blood spraying between her fingers. Eyes wide with shock, she drops to her knees, then flops over on her back, kicking convulsively and making horrible gargling noises." A round or two later I might mention that she's *still* kicking and gurgling, and do they want to put her out of her misery or heal her for interrogation?