I thought in Carlsen but this one but "His next world champion was considered as underdog during championship." Fischer had a more sad past. Therefore my answer is Fischer. Ding Liren was also an underdog because Carlsen didn't defended his tittle but he doesn't have an universal style of play on the board.
Solution to guess the player day 7
Rashid Nezhmetdinov
Guess the player day 8
•A world champion
•Often called by people to be first one with universal style of play
•His next world champion was considered as underdog during championship.