Synonyms for Knock-down:

adj.

all (adjective)
powerful.

n.

decrease, lower, top-slice, erode, halve, shrivel, minimize. deceive yourself, push aside, dismiss, close your mind to something, put your foot down, ignore, not hear of it, spurn, turn down. demolish, condemn, wreck, gut. flatten, lay out, punch someone's lights out. ravage, destroy, devastate, trample, damage. knock out, drub, thrash, HIT, beat. knock-down (noun)
powerful, strong.
knock down (noun)
cut down, deck, dump, pull down, floor, coldcock, push down, down.

Other synonyms:

demolish. condemn, destroy, wreck. gut. lay out. level
flatten.
Other relevant words:
condemn, trample, drub, down, destroy, decrease, coldcock, gut, spurn, dump, deck, thrash, ravage, shrivel, wreck, beat, halve, ignore, minimize, dismiss, floor, erode, HIT, devastate, demolish, top-slice, flatten, lower, damage.