And watching the humanity drain out the characters when new writers would take over was always the saddest part of the transition. JB would run the perfect lap, skillfully pass off the baton, and they'd just stand there and fart.

He changed, removed or killed off so many characters that by the end of his run he really was painted in to a really bad creative corner.

His retcons on the backgrounds of Northstar and Aurora were terrible, he wrote Shaman and Talisman out of the series for no good reason, killed off Box and Snowbird and resolved the Sasquatch resurrection problem in a terrible way that sacrificed Snowbird for it.

I find it interesting that, after JB put so much time into making Alpha Flight into a very fluid understanding of what it means to be a superteam, that Mantlo would immediately reverse those changes, and make them Canada’s Avengers for a while. 

Later, he dismantled them again, and left it kind of unclear how this team operates best – as a defunded group of individuals spread across a vast country, or as a traditional team where everyone lives in the same awesome mansion.

His additions / replacements were terrible. Laura Dean, Goblyn, Purple Girl, and Manikin. Taking Madison Jeffries from being a shy version of Ben Grimm to being the backbone of the team?!

The most memorable things of the Mantlo run were; Heather becoming Vindicator (which I think was a wrong move), revamping Yuriko Oyama in to Lady Deathstrike and the debut of Jim Lee to Marvel.