4x32 - Dragon Ball Z: Dragon Box

Vegeta's pride reacts to Cell's claim that if he could attain his perfect form, he would not be beaten. As a result of the Saiyan instinct to fight ever-stronger opponents, Vegeta chooses to allow Cell to have his perfect form. Ignoring Trunks' attempts to stop him, Vegeta allows Cell to get away. As Cell escapes from Vegeta's ferocious attack, No. 18, whom Cell had been searching for, appears in his line of sight!