Kweon Haekwang (aggressive) lost his first game on KGS

Kweon Haekwang (aggressive on KGS) was undefeated in even games till April 17, but on that day he lost 2 games straight - both of them to bigbadwolf, famous American master.
Here is the second game they played.
Black's losing move: tennuki at 19 - it was necessary to defend on the top.
White's attachment is the standard tesuji in such situation and the right punishment. Black lost the whole corner and later he did not have any chances