Among other things, he flat out lied during the Brexit campaign and has single handedly rejuvenated the separatist movement in Scotland, Wales and could end up being responsible for the reunification of Ireland. In short, the end of the United Kingdom.
Britain had the highest number of Covid deaths in Western Europe, largely to his scatelogical approach, exemplified by party gate. People don't appreciate making sacrifices and lock downs when the PM and his circle are partying. He was fined by police for breaking his own rules. The only time that has happened to any PM.
The UK economy is in the tank. UK inflation is 9.1% and the Bank of England expects it to exceed 11% by October.
https://en.wikipedia.org/wiki/List_of_departures_from_the_second_Johnson_ministry