Thanks Brett,
I voted for El Alamein by the way. Monty's victory over Rommel was an important turning point in WWII. The battle completely destroyed the German's strategic initiative against the western allies. Plus it was very much a Commonwealth effort what with all of the various formations representing multiple nations at this particular battle.
1956 - Hungarian Revolt
1968 - Prague Spring
1988-91 - Eventual Collapse of the Soviet State
Some of the 1848 Royalist suppressions, especially in the Austrian Empire, were particularly reactionary and IMO bear resemblance to the Soviet Armed Response to the uprisings in the Eastern Block during the Cold War.