He slowed.
( He ( slowed . ) )
(ROOT (S (NP (PRP He)) (VP (VBD slowed)) (. .)))
He stopped moving so quickly.
( He ( ( stopped ( moving ( so quickly ) ) ) . ) )
(ROOT (S (NP (PRP He)) (VP (VBD stopped) (S (VP (VBG moving) (ADVP (RB so) (RB quickly))))) (. .)))