Synonyms for Looter:

n.

looter (noun)
freebooter, pillager, plunderer, despoiler, spoiler, raider.
marauder (noun)
freebooter.
plunderer (noun)
spoiler.
raider (noun)
raider.
thief (noun)
plunderer, raider, pillager, spoiler.

Other synonyms:

Other relevant words:
despoiler.