This is the Endgame trilogy by James Frey & Nils Johnson-Shelton.
From a review of the first book:
The premise of Endgame: The Calling is that the end of the world is at hand. Twelve thousand years ago early humans were given the spark of intelligence by aliens. Now, the aliens have returned to see how we turned out. Twelve ancient civilizations passed these secrets down through the generations, always with a young warrior ready to battle should the need arise. Known as The Players, teens in each culture have spent their youth training for this final battle. There are three keys to be found (corresponding to the three planned books in this series) with the final key being the one that saves all the descendants of the winner’s civilization.
The first few chapters of the book introduce the twelve players. Some are seasoned martial arts experts, others are skilled computer hackers, others weapons experts, and some with other specialties. A bunch of teenagers fighting to the death with all the resources they can acquire gives the story a Hunger Games meets James Bond feeling. I suspect this novel will require more suspension of disbelief than many readers will be willing to give it.
With such a large cast of characters, the authors wisely chose to focus the story on a few characters, namely Sarah Alopay of the Cahokians of North America, Jago Tlaloc of the Olmec of Peru, Chiyoko Takeda of the Mu of Japan, Baitsakhan of the Donghu of Mongolia and An Liu of the Shang of China. Although she doesn’t get the most page time, the most interesting character was Chiyoko. First, because she’s mute, and second, because her civilization is based in myth. Many of the other characters seem to have unlimited resources such as transportation or money or safehouses or weapons caches. Chiyoko has some weapons, but her other resources seem very limited. She’s got to depend on her ingenuity and disguises.
From the Endgame Wiki page for An Liu:
An Liu is referred to by most of the other players as a madman, and that much is true. He excels in hacking and bomb-making, but he is also a good close-quarter-combat-fighter, and able to handle a Butterfly-knife. He has nervous tics, blinks and shivers, and stutters. He has a tattoo of a red tear on the edge of his left eye. He is in love with Chiyoko Takeda, as only she can make his tics stop, and allow him to speak calmly. After Chiyoko's death, however, he crafts a necklace out of her hair and ears in order to stop his tics. In Rules Of The Game, An begins to hear Chiyoko's voice (although she is mute) in his mind. He then becomes, perhaps, even more mentally disturbed than he was before.
In his hideout in Japan he is attacked by the CIA-Death-Commando of Aisling Kopp. He wakes up at the right time, because Chiyoko warned him in his dream, shoots one of the infiltrators and blows up the whole Harbour-complex with a dirty bomb. Only Aisling and Pop survive, whereas the whole Death-Commando gets killed.