Originally Posted by PhailRaptor
Sadly no. The strongest item slow and the strongest spell slow will take priority at any given time. Frozen Mallet is a stronger slow than BroFist, so Frozen Mallet will take priority over BroFist on the target.
How do you of all people not know that ALL SPELL SLOWS STACK, EVEN THOSE FROM ITEMS? This hasn't changed for years. The only non-stacking phenomenon that occurs is that passive slows DON'T stack; which applies to Frozen Mallet, Phage, Trinity Force and Rylai's. Randuin's Omen's passive slow get's a free ride because it's a defensive slow.