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Acks are red enemies with sharp teeth that first appeared in Donkey Kong Country Returns. They are found in the fifth level in the Ruins world, Itty Bitty Biters. They are related to Toothberries, AckStacks and Cageberries. Acks are more aggressive and bigger than normal Toothberries. They also require two jumps to be defeated, while Toothberries only require one. Alternatively, a Kong Roll will destroy one with a single hit. To attack the Kongs, Acks attempt to jump on them. Their jump is the highest out of all their relatives. If Donkey Kong and Diddy Kong make contact with these biters, they will lose a heart. Acks also appear in the Forest level, Clingy Swingy.
AckStacks are yellow Acks that appear as a tower and attack as a group.