Ed pointed out a joseki mistake by B in the upper right corner, which gave W a locally superior result. But this tactical mistake was small compared to the strategic mistake W made in allowing the lower right group to come under severe attack.
The sequence
through 
let B make territory while W played dame. Now B is in control of the game. At move 33, I think B should just hane at O9 and continue to make territory while attacking. Things are going well, so there is really no need to start a confusing fight.However, B picked a fight and outplayed W in that fight. When W resigned, the game was hopeless. It looks difficult or impossible for W to save the big group of surrounded stones, and the W side group is not yet alive.
If you want pointers about the fight,
was bad. If you decide to save the cutting stone, just play N7 directly without losing liberties. You could also simply give up that stone in exchange for sente moves like P4 and O9, then win on territory without a big fight. Note that if B defends against the cut at R9 (say by playing O9), then the W side group needs another move to live.