should have been a painless time-killer 
(ROOT (VP (MD should) (VP (VB have) (VP (VBN been) (NP (DT a) (JJ painless) (NN time) (HYPH -) (NN killer))))))
(ROOT (VP (MD ) (VP (VB ) (VP (VBN ) (NP (DT ) (JJ ) (NN ) (HYPH ) (NN ))))))