Although I saw that Tailwind has been scrapped as a slash, I think it's still worth mentioning in the moves section, if not brought back as a slash. It's not a bad move, per say, and giving Tailwind to something like Mega Garchomp or Mega Heracross can be seriously game changing. If there are no setup sweepers on one's team, then Memento is a tougher sell than Tailwind IMO, because the main point of Memento is to weaken something so that you can set up in its face with another Pokemon. On the other hand, Tailwind is great when you have a decently bulky, very powerful attacker with below-average speed. I really think it depends on the team composition to choose between Memento and Tailwind.