( He ( ( ( ( climbed ( ( ( 8611 ( m K2 ) ) , ) ( the ( second highest ) ) ) ) and ) ( according ( to ( ( many , ) ( ( the ( ( most ( ( difficult and ) dangerous ) ) mountain ) ) ( of ( the world ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (PRP He)) (VP (VP (VBD climbed) (NP (NP (CD 8611) (NN m) (NN K2)) (, ,) (NP (DT the) (JJ second) (JJS highest)))) (CC and) (VP (PP (VBG according) (PP (TO to) (NP (NP (JJ many)) (, ,) (NP (NP (DT the) (ADJP (RBS most) (JJ difficult) (CC and) (JJ dangerous)) (NN mountain)) (PP (IN of) (NP (DT the) (NN world))))))))) (. .)))
He climbed 8611 m K2, the second highest and according to many, the most difficult and dangerous mountain of the world.
(ROOT (S (NP (NNP K2)) (VP (VBZ is) (NP (NP (DT the) (JJ second) (JJS highest) (NN mountain)) (PP (IN in) (NP (DT the) (NN world)))) (, ,) (PP (IN at) (NP (IN over) (CD 28,000) (NNS feet)))) (. .)))