Definitely made a lot of mistakes in the time but letting Vinicius go is probably my biggest regret, with swapping Kimmich for Trent and Bellingham on par with signing Mbappe uncontested for the best deal.I mean the United dominance is sickeningly admirable.
To be on top for so long the wheeling and dealing must have been epic.
I started off at Leeds United in season 1, already well on my way to building the squad when Zarlak left United in season 2(?). Took over there but made the choice to uproot a fair chunk of the side he built as, while a lot of the players were high rated, they were also very old and had to make some decisions very quick like selling Buffon and starting De Gea when he was still developing as he was getting playing concerns.
Hardest bit is knowing when to rebuild and making the moves before it is too late. It is certainly a lot tougher these days. I think I've done a good few successful rebuilds but the current one isn't going so well.