If you have the Forgotten Gods expansion and have a character who can access that in Ultimate difficulty then you can buy Merit Tokens to allow other characters to skip the lower difficulties and start on Ultimate. It’s quite a bit harder mind you because you still have the resistance penalties you get on Ultimate, but you do get the skill/attribute points you would have gotten from quests on the lower difficulties.
Alternatively, just use a blank L100 character to make it how you wish.