Discord. It takes like 12 seconds to start each time I launch it. Of course it's plenty fast after that, so I guess it's just the startup time that's slow.
Imo the frequent updates aren't that bad since they aren't "mandatory" in the sense that they force you to quit and reopen in order to have base functionality. And since I realistically don't actually open discord more than once per day since it's just in the background, the extra couple seconds isn't really an issue.