either/both as you like

yeah she's not really a commander, she's someone who goes in a Grixis commander deck

or, say someone counters one of your spells with a super-deluxe counterspell like Sublime Epihany or Counterpoint. you don't want them to get all the benefits of killing your spell, so you put Ogrek's ability on the stack at instant speed, and now they get nothing for nothing

like, for comparison sake, consider Ultima, which boardwipes and then ends the turn. Persist triggers, undying triggers, "when this creature dies you draw a card," etc - none of that happens because Ultima ends the turn.

the most obvious use is "I want to kill something but I don't want that creature's death reaction trigger to fire off"

That's just the milder version of "is this person dead now" and I much prefer wondering which of them descended into normie mundanity

"I wonder if that girl dancing like there's no tomorrow at 2:37 of the video is now a member of her HOA"

remember.

idk not to mention how very nuanced and normal the actual response here was

something with a duck on it somewheres (not a real duck, a picture of a duck. unless you wanna go real duck)