Complement1[l1, l2] where l1 and l2 are lists returns a list of elements from l1 not inl2. Multiple occurrences of an element in l1 are kept and multiple occurrences of an element in l2 are dropped if present in l1.
Complement[{a, b, c, d, e, f, e}, {a, b, c, d}]\{e,f\}
Complement1[{a, b, c, d, e, f, e}, {a, b, c, d}]\{e,f,e\}