Green’s Dictionary of Slang

doer n.2

[do v.1 (2a)/SE do]

1. a cheat, one who defrauds another.

[Aus]Table Talk (Melbourne) 7 Oct. 34/1: A great colt and a great ‘doer’ is Strathredole. / He ‘did us’ for nearly a hundred on Saturday. / He’s a great ‘doer’ all right, but he won’t ‘do’ us any more.
[UK]Partridge DSUE (8th edn) 322/2: from ca. 1840.

2. (Aus.) a character, an eccentric, one who never gives up despite any circumstances; often intensified as hard doer under hard adj.

[Aus]Table Talk (Melbourne) 7 Oct. 34/1: A great colt and a great ‘doer’ is Strathredole. / [...] / He’s a great ‘doer’ all right, but he won’t ‘do’ us any more.
[Aus]W.H. Downing Digger Dialects 19: doer (n.) — A person, usually humorous, reckless, undisciplined, immoral or eccentric.
[Aus]K.S. Prichard Coonardoo 300: You know Monty, damned old hard case, one of the hardest doers in the Nor’-West.
[US]D. Runyon ‘Lonely Heart’ in Runyon on Broadway (1954) 493: Moreover he is a pretty good doer, at that.
[US]J.A.W. Bennett ‘Eng. as it is Spoken in N.Z.’ in AS XVIII:2 Apr. 88: A doer is a jester, or an eccentric.
[Aus]D. Stivens Jimmy Brockett 140: Bit of a doer was young Herb, particularly with the little tarts. He did pretty well for himself, though most of ’em weren’t my meat. No style about them.
[Aus]A.W. Upfield Bony and the Mouse (1961) 69: ‘Hard doer, ain’t he?’ grumbled the council staff.

3. (US) a criminal.

personal correspondence 7 July: doer (US) criminal. Seattle police slang. My first sighting was in a 1999 novel by Ridley Pearson, with no suggestion that it was a new usage.