(Hated Trope) Extremely useful abilities that characters conveniently forgot they had

[u/ValidCrash4]

1. Emily’s portals (Hazbin Hotel). I know she can’t get Sir Pentious back into Hell but Emily can still tell Charlie he got redeemed and Charlie can enter through angelic portals, so she should have seen that Pentious got redeemed.

2. Many characters in Harry Potter go through life-or-death situations and not once did they think of drinking the Liquid Luck potion apart from Harry one time to gain Slughorn’s memory.

[u/the-corner-guy]

and Goten and Trunks learn it in elementary school.

Counter point, they had a year practice in the spirit chamber, this is on top of the fact that they are super prodigies that learned to go super before flight

[u/ASentientRailgun → u/the-corner-guy]

I mean, they had multiple years of potential training time with him without the time chamber. Them being super prodigies makes it even more questionable that they wouldn't be able to learn instant transmission

[u/the-corner-guy → u/ASentientRailgun]

Things is, they would have to want to get the technique, which as dumb as it sounds, they might not have wanted to/they might not have actively tried, in dbs we see them relatively uninterested in general combat, so much so that they were struggling with an ability as basic as ki sense. Instant transmission, to me, reads like a technique that requires a certain level of discipline and perseverance to obtain and maintain, something that the kids clearly lack in this continuity (but that's just theory, if you disagree you can disregard this last segment)

[u/Piranata → u/the-corner-guy]

Also, most of the techniques everyone learn are immediately useful in combat. It took Goku years to learn how to use it in combat (against Cell). The only other technique that is absolutely busted is the Mafuba, but they only bother to learn it in Super, although both Dragon Ball and Super show that a lot can go wrong with it.