Against Alduin I wanted it to feel really heroic, so I finished him with a sprinting attack wielding a greatsword.
Mercer's treachery should be answered with the most cruel death, so I soul trapped him and stored the black gem in a chest.
When killing the Emperor, I remembered Arnbjorn's words: "Make it bloody and spectacular". So I killed Mede with a biting attack in Vampire Lord form.
Commander Maro died by the Blade of Woe.
And so on.