Who would win in a fight: an amoeba or a leukocyte?
Assuming you don't mean a single leukocyte as I doubt That a lone leukocyte could do much. Macrophages and neutrophils can release their lytic/degrading enzymes spewing them on to the amoeba. Antibodies produced by BCells, particularly the IgE type can coat amoeba and cause histamine release from mast cells recruiting more neutrophils and macrophages. Eosinophils are also important. Finally one must not forget the complement system, a series of proteins that could kill by making pores in the amoeba membrane. Amoeba have however developed many techniques for immune evasion, such as diverting the immune system via cell signalling (cytokines) such as IL10 which dampens the immune system or coating themselves or activating the "wrong" immune system.