Using cartridges on the N64 instead of CDs, which resulted in overpriced games, poor rendered graphics, extraoedinarily high dev costs, and no one developing games for it outside of Nintendo and Rare. It finally wnded with Nintendo losing two full generations of consoles. Among the lost was Square, which was probably Nintendo's second most important dev partner (next to Rare).
Also the GameCube was a fairly big mistake, the system looked like a purple lunchbox, had no great software aside from some Dreamcast ports/remakes an a couple resident evil games and they lost Rare (not even all of the exclusive GameCube games combined made up for the loss of Rare), and everything had to be played with that monstrosity of a controller.
I describe myself as a little dose of toxic masculinity.
