9. Darth Vader Killed Five Imperial Officers
Granted, Vader force-choking five random Imperial Officers may seem like quite a step down from him curb-stomping a kaiju. However, given the circumstances around it, Vader's brutal murder of these unfortunate souls acts as a terrifying reminder of his level of authority in the Palaptine's Empire.
This incident takes place early on in Charles Soule's Darth Vader series. Soule's stories focus on the early days of Vader's apprenticeship with Palpatine, neatly dovetailing with the embryonic stages of the Galactic Empire.
Vader is initially regarded as a rank outsider by the Imperial brass, and one whose unknown influence they would rather see removed from their neat, orderly chessboard. This leads to several, predictably futile, assassination attempts against the Dark Lord, resulting in Vader having to lay down the law. Vader and Palpatine assemble a meeting of all high-ranking Imperials, where Palpatine makes clear that Vader is his right-hand man and that Vader's actions - whatever they may be - all carry the Emperor's seal of approval.
Vader chooses to illustrate this fact by executing five randomly chosen Imperial officers. He doesn't know or care if they had anything to do with the attempt on his life - he just wants to make clear that any more attempts on his life will be met with similar reprisals.