After Goku beats Frieza, the galactic tyrant was found by his father King Cold who gave him metal parts making him Mecha Frieza. In this story, Future Trunks is not there to stop him, making Devilman the hero. Devilman fights Frieza, who then lets his henchmen, including Appule, to finish the job. Devilman kills the henchmen and destroys Frieza with the Devilmite Beam. King Cold, in absolute anger, attempts to annihilate Devilman, however, Devilman still finishes off King Cold with the Devilmite Beam, laughing afterwards.
If Frieza or King Cold is defeated without the Devilmite Beam, the dialogue Devilman says will be "Bad end, hahaha."
If King Cold is defeated with the Devilmite Beam, Devilman will say a short and unusual monologue. He appears to be racing against time for some unknown reason and seems confused himself, before eventually deciding to let whatever was on his mind go with a simple "well, whatever."