I'll make a safe one - regardless of who wins, about 1/6 of the country is going to lose their fucking minds and claim the election was "stolen" or some similar language indicating that the win wasn't legitimate. If Harris wins it will be "stolen", if Trump wins they will use a different word because calling an election "stolen" is right wing and thus icky.
Regardless of who wins, there will be recounts requested in at least two states and lawsuits filed regarding the election in at least one - these numbers will be much higher if Harris wins.
Put odds of a riot if Trump wins at about 50/50, odds of a riot if Harris wins at about 75%.