I left you this position:
After the moves 30.Qxa6!? Rxc1+? 31.Rxc1 Rxa6 32 Rc8+ Qe8! Karyakin continued 33.Rxe8+ Kf7, giving the next diagram:
Now he showed the point of his combination, with the wonderfully spectacular 34.Ra8!!, which forced immediate resignation.
For a bonus point, I asked which ex-world champion had used a similar idea to win a famous game in the 1960s? The answer is Mikhail Tal, in his game against Brinck-Claussen, from the 1966 Havana Olympiad.
In the diagram position above, Tal won material with 33.Nxd5! Bxd5 34.Ra8!!
It would be interesting to know if Karyakin was familiar with the Tal predecessor. The young Karyakin was certainly capable of finding his combination against Kosteniuk by himself, but, on the other hand, the Tal-Brinck Claussen game is well-known, because it featured in a widely-published article Tal wrote, based around a 1956 game Polugayevsky-Tal, in the same opening line.
Either way, it is a spectacular tactic, which never fails to delight.