Nick Kostreski is an aerospace engineer from Silver Spring, Maryland, best known for his nickname, the KO Ninja.

American Ninja Warrior 8

Nick first competed in Philadelphia in American Ninja Warrior 8. His run in qualifying was cut, but he was one of the many competitors that failed Rolling Thunder. Nick placed 22nd and moved on to the city finals, where he made it past the Rolling Thunder but fell on the Flying Shelf Grab. Kostreski managed to place 12th overall and advance to the national finals. Unfortunately, on stage 1, Nick timed out on the Rope ladder after getting hung up on Sonic Curve and missing his first attempt on the Warped Wall, hampering precious time.

American Ninja Warrior 9

Nick returned to compete in Denver in American Ninja Warrior 9 where his run was digested in qualifying but he was one of only eight athletes to finish the Denver qualifying course. He had the slowest time out of all finishers, placing 8th. His run in the city finals was also digested, but it was shown that he failed the Wedge when he made a mental mistake and hopped the bar out of the panels. He still placed 15th overall and made his second trip to Vegas.

In Stage 1, he was cut but it was revealed he cleared the course with 17.72 seconds left. His run was digested in Stage 2, but it was shown he failed the Wave Runner when his board became off balance while readying himself to transition.

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