Cartoon Network vs Power Rangers
Connection:
Both are megalomaniacal, ancient alien villains with green skin and red eyes, who's missions involve seeking out objects that landed on Earth that allows its user to transform into powerful beings. (The Omnitrix allowing its user to transform into aliens and the Energems allowing its user to morph into a Power Ranger)
Both would come down to Earth in an attempt to take it from young heroes who became the holders of them (Ben Tennyson and Dino Charge Rangers respectively), leading armies that they built themselves over the years
Both also hold a grudge against the older mentor to the protagonists as they have a history with them. (Max having fought Vilgax in his past as a Plumber and Keeper having been on the run from Sledge for a long time)
Despite their ruthlessness and cunning, both do have people they genuinely care about, partly doing what they do so they can gain their affection (Vilgax's people and Poisandra respectively)
Both were eventually defeated and seemingly died, but came back multiple times as major villains, even teaming up with another villain (Albedo and Arcanon respectively), but ended up betraying them
