The first John Steed /The Avengers comic ever was The Drug Pedlar, a series 1 comic featuring John Steed and Dr David Keel. The comic was released in The Crimbusters Annual from 1962 (pages 87-92).
The newest John Steed related comics were produced by BOOM! Studios in 2014 as Steed and Mrs Peel - We're Needed, six issues were planned, three have been published so far.
Mike Noon started to collect information about The Avengers comics on his site The Avengers Illustrated and J.S. Ferguson concentrated on The New Avengers related comics on the TNA focused site ANew.
Denis Kirsanov, webmaster of Steedumbrella, combined these information and completed the comic section with missing pieces and the newest information about The Avengers comics.
For a list of The Avengers comics sorted by country of it's publication go here on Steedumbrella. There are comics from The United Kingdom, The USA, France, West-Germany, Netherlands, Agentina, Spain, Chile, Belgium, Austria and China.
Parody in "Pilote. Le journal qui s'amuse a reflechir", Vol. 13 Issue 583
see on: Le Monde des Avengers
3. Ian Durden's The Avengers comic strips
Artist and The Avengers fan Ian Duerden published several The Avengers comic strip on his website The Avengers Artland.
The Annual Illustration Strips:
The Late Christmas Present
The Christmas Rose
On the Feast of St. Stephan
Under the Mistletoe
The Comics Strips
and don't forget to make the aquantaince of the dashing hero Calamus Quill in
The Tales From the Clockwork Empire (two volumes).