Immensely powerful and terrifying tyrannical alien entities who threaten to destroy the entirety of existence. When young, they were both taken care of by a member of another species (Gamzee Makara and Maria), but as they grew older, they became exceptionally powerful beings who could manipulate with the fabric of time itself, and used to go back in time, before they technically even existed to perpetuate their plans in destroying reality. Both have employed a variety of other entities acting as agents, including a group of prominent, loyal aliens that also have time powers (Leprechauns, which most of the Felt in particular consists of, and the Starmen). Both have faced off against young, plucky adventurous 13 year old boys (John Egbert and Ness) and their group of friends, as well as involving themselves with people who are essentially their precursors (Caliborn messing with the Alpha Kids and Giegue fighting against Ninten and his friends). Both in some way use an ominous, humanoid inanimate object to further their goals (The Mani-Mani Statue and Lil Cal). Both can only be defeated in specific ways (Lord English only being able to be destroyed via a few time-based glitches and loopholes and Giygas only being able to be defeated via praying). Both are also noted to be not really be all-there mentally speaking (Lord English is very mentally immature and Giygas is pretty much insane and completely mentally broken).

Yes, I did make this because John vs Ness exists