Dragon Ball Z - episode 81 - 05 Mar, 1991

Piccolo and Frieza begin to fight and with his new power, Piccolo is able to hold his own with Frieza. Also, since he is fused with Nail, he is familiar with the way Frieza fights. Inside the isolation chamber in Frieza's spaceship, Goku senses that Piccolo has arrived, and that his strength has dramatically increased. It seems that Piccolo is going to defeat Frieza. (Source: Wikipedia)