Once I saw someone tweet that their pet peeve was ‘magic without a cost’. By that, they meant stories where people perform their magic and there is no counter-balancing negative effect.
But that doesn’t worry me so much. I see magic as akin to wisdom..they (the character) has learned this or that and now they are empowered, much as we all become empowered as we age.
My pet peeve is when the magic is unearned. A character gets “magic” and, boom, they know how to use it. No training. No time spent.
The Doctor Strange and MCU movies very cleverly get around this with time suspension and studying in the astral plane (while asleep). Just one of the many, many reasons that movie is brilliant, IMO.
Anyway, unearned power for a character doesn’t kill a story for me—but it downgrades it a tad.