Peaky Blinders: The Worst Thing Each Main Character Has Ever Done

Whilst it can be argued that Arthur beating a boy to death in the boxing ring is the worst thing he's ever done individually, it is his capture and mercy killing of Vincente Changretta that had the biggest impact on his family.

After Grace Shelby is killed by Vincente's men, when they were actually after Tommy, Arthur and John are dispatched to get Vincente and bring him back to Tommy, so that he may slowly kill Vincente.

In an act of mercy, Arthur kills Vincente before Tommy can inflict pain upon him. Unfortunately, this kicks off the vendetta that would see John killed at the hands of Luca Changretta's soldiers.

More than that, Luca's vendetta brings down Alfie Solomon's operation and forces the Blinders into retreat against the might of the New York Mafia. Michael Gray ends up getting shot and almost killed by Luca's men, whilst Luca himself chases Tommy through Small Heath with a machine gun.

By the time the vendetta has ended, it has cost the Shelby family some of their allies, a lot of money, John Shelby, and much of Arthur's sanity.

It might have been at Tommy's orders that Vincente die, however, it was Arthur who pulled the trigger.