The fix might differ according to the reason they hate you. Is it because they're a different culture/religion?
If they're a different culture: educate your heir with a man of the right culture, or outright culture convert (as an unreformed pagan you can change your culture to the one in your capital. And your religion as well.)
If it's short reign: tank it, improve legalism, improve relations.
If it's traits: educate your son well (kind, patient, just, etc...)
Desire titles/too many titles held: sort out your mess
All: give them gifts using money from raids, prestigious useless titles (hirdman, cupbearer, etc...), and use your chancellor.
If you have enough power, bury people who hate you under grateful dukes, that generally works out well.
Failing that, kill them and hope their son like you better.
Revoking for no reason increases tyranny and makes them hate you more. On the other hand people you appoint after that don't have the tyranny penalty and are grateful for the titles, so you could revoke a handful of strategically placed counties, appoint new count there, and make them dukes, burying the remaining angry counts under them.
Why did you let two vassals control 90% of your kingdom?
his kingdom is mostly single-counties counts and a single duke, I don't see what you're talking about?