Assignment's rhymes with:
assignments, reassignments, assignments, reassignments, alignments, assignments, realignments, reassignments, refinements, abandonments, alignments, arraignments, assignments, entertainment's, entertainments, environment's, environments, governments', postponements, realignments, reassignments, refinements
Assignment's sounds like:
accents, accentuates, accommodates, account's, accounts, acmat's, agematsu, agendas, agent's, agents, agents', aquanauts, ascends, asmodeus, assessments, assignments, axiomatic