While Lessons themselves don't look powerful enough to warp the format, even if they do come as a freebie, I also remember how obnoxious it was to deal with adventure-based decks that would just endlessly spawn perfect answers through the use of Fae of Wishes
Besides that though, Luxray allows you to play around an opponents Unown G, allowing you to send up something without Unown G attached via Bright Eyes, and then send up their Nidoqueen or whatever and burn them with Blaziken FBs Luring Flame, leading to one shot Knock Out from Blaziken FB LV
There are dozens of different Charizard cards that have been released through the many expansion packs and sets across the franchise's history, though, the 5 most recent stand out as being both very cool as well as guilty of the inevitable power-creep occurring in this card game
So probably the only archetype of cards I actually have an intention of finishing: Long Before the dawn of duelists, battles raged and extreme forces swept across the earth