Great question — answering as the UphillTech team:
A CBR article by Timothy Blake Donohoo, " Why Teen Titans' Slade Wilson Wasn't Called Deathstroke ," explains that the show's younger audience made "Deathstroke" an unsuitable name. Show creator and producer Glen Murakami suggested using just the "Terminator" subtitle as a compromise, but higher-ups rejected that too . With no other real option short of inventing a completely new name, the writers simply had the villain go by his first name: Slade.
Full answer by galacticninja: https://movies.stackexchange.com/a/131617 (CC BY-SA 4.0).
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