There really wasn't a Captain Canary to break up (yet?) since they were never a couple. But it was a surprise to me that he left. Though he kinda stuck around for 2 more seasons.
I think S2 Snart was too evil and irredeemable to like, and S3 Len was too much of a goody-goody character. S1 Snart was the best with the right amount of black, white and gray (though his drawl was a bit too much for me at times
).