The TVTropes Trope Finder is where you can come to ask questions like "Do we have this one?" and "What's the trope about...?" Trying to rediscover a long lost show or other medium but need a little help? Head to Media Finder and try your luck there. Want to propose a new trope? You should be over at You Know, That Thing Where.
First one might be covered by Laser-Guided Karma or Hoist by His Own Petard, although I feel like what you're describing is a more specific trope that I don't think exists yet. Might have to take it to YKTTW.
The second might be The Bad Guy Wins meets And Then What?.
Thanks. Hoist by His Own Petard is in a way close but associated with villains rather than heroes. Might be worth heading over to YKTTW with it I guess if I can scrounge up more than one example.
And I think I managed to find what I was looking for from And Then What?. It's probably a subset of Pyrrhic Villainy.
Edited by whereismytea
The third one is one I'd be interested to find as well. When I was writing a story I toyed with the idea that the protagonist's love interest had actually seen her before, when she was very young. There's also a case of this in Fruits Basket, where one of the Sohmas (I'm not saying which, it's a bit spoilerish) led her home when she got lost. Although that's more of a case of her never knowing who it was to begin with, rather than forgetting. Similar principle though. Kinda reminds me of One Degree of Separation.
@Nori Mori: I've started a ykttw for it here, since I still haven't turned anything up. Feel free to drop by with your Fruits Basket example!
https://tvtropes.org/pmwiki/discussion.php?id=4a9cags21bqi272vrawzehvj
Scratct that, someone did find it: Forgotten First Meeting.
Feel like there must be something that covers this:
Someone's testing out their powers on something inanimate, or something easy enough to kill, but after the first hit it seems like it didn't work, so they step closer to check on it and as soon as they are in range that's when the cliff crumbles or the avalanche falls etc. Basically a delay happens between the attack and the result during which the hero foolishly moves into the danger zone because they think it didn't work.
Also, do we have a trope where the Big Bad is basically successful, has defeated the heroes, and then just decides to retire?
Edit: I seem to be having the worst day with finding lost tropes. Do we have something for people who become friends later in life but actually met before (usually years ago) and one or both forgot. Like a second first meeting?
Edited by whereismytea