Say what you like about Campbell, but his beatdown of Arthur and his rousting of the Bolsheviks show his effectiveness and what an intimidating presence he is.
Polly showing what a stone-cold badass she is in 1.02 - first, she psychs out Campbell by refusing to be intimidated by his manhandling her, instead kissing him because she knows it'll unnerve him. Second, she stands up to Tommy about Ada and confronts him about fixing races behind Billy Kimber's back, even takes a fireplace poker to threaten Tommy with when he burns Ada's letter to Freddie.
Tommy's bonfire designed entirely to get up Campbell's nose. He even invites a reporter from the Birmingham Dispatch to paint himself as a war hero and Campbell as an invader, the resulting article going straight to Churchill, who calls out Campbell for his failure.
Tommy's long-con on the Lees, proposing an alliance with Billy Kimber against both the Lees and Campbell's investigation.
Ada's response to Tommy asking her who the father of her child was: "Rudolph Valentino". As Tommy himself says, no one dares to so much as look the wrong way at him, and here Ada is, sassing her extremely volatile gangster big brother.
Ada running through Peaky Blinders territory in her wedding dress. If that isn't the biggest "fuck you" to her brothers in existence, I don't know what would be.
Polly vs. Grace at the Garrison. The entire damned scene, starting with Polly telling Grace they all know about her and drawing her hairpin out. Grace pulls a gun on her, dispensing with the "sweet innocent barmaid" act, which doesn't faze Polly a bit, and she continues telling Grace precisely what she is, a narc, an Ulster girl who hated low people like Polly until she met Tommy. This strikes a nerve with Grace and she puts her gun down, threatens Polly with her fists - to which Polly laughs, replaces her hairpin, and tells Grace to pour them a whiskey, they're more civilized than that.
Polly: But I should tell you this - I will never forgive you, or accept you, or take you in. And it's me who runs the business of the heart in this family. As far as I'm concerned, you're a snitch from the parish, and if you're not gone from this city by tomorrow, I'll kill you myself.
The battle between the Peaky Blinders and Kimber's men isn't won by either side, but by Ada Shelby, pushing her baby carriage into "no man's land" and telling Kimber off for trying to kill her brothers and husband. It's ruined by Kimber getting a little Trigger Happy, but the fact remains that Ada fucking Shelby faced down two dozen trained gangsters bent on killing her family, and she won.