My personal favorite for flawed reasons is Madoka because I was there for the live reactions to the infamous episode and it was magical watching everyone lose their shit. It was also my re-introduction to anime after being shamed out of it for liking sailor moon as a kid.
Big fan of Madoka myself! I went in blind years after it came out, more shocking than the ending of gambo tbh.
As far as deconstructions of games go, Undertale is up there as one of the greats. The route that most blind players will take will be to get the neutral ending and then go back and get the pacifist one (then go back again and get the real one), but the more you go for completion the more the game begins to judge you. You learn that the villain Flowey is literally a completionist who is bored and acting evil to see what will happen - and then if you follow in his footsteps you become more evil than he ever was, all just to see what will happen.
Deltarune is attacking the fourth wall from a slightly different direction, with the player and the main character seemingly in a struggle for control over the game. It's neat, but until it's finished it's hard to say if it will surpass the original.
Madoka is great but still i would hold back from the deconstruction label. Dark and fucked up magical stories in the magical girl genre existed before, Madoka just executed greatly while being towards the most fucked up side of things available. Dont think its a deconstruction tho
That all sounds dope as hell. Would you rec one over the the other to start with? Madoka was one of my first anime so it kinda spoiled me, but on the plus side I’ll always enjoy a new show by gen.