Marvel Comics vs DC Comics

Connection:

Both are comic book alien villains who are characterized and driven by their insatiable sense of greed and desire to overtake everything for themselves

Both primarily reside in cosmological areas off-limits to most other characters (the Vega Star System and the Negative Zone respectively), which they themselves only leave for the purpose of invading and conquering other areas

Both possess many similar abilities courtesy of wielding an incredibly powerful and versatile weapon (Cosmic Control Rod and Orange Lantern Ring respectively) such as creating constructs, telepathy, flight, draining and stealing other's energy/life force, teleportation, etc.

Both have a means of technical immortality (Annihilus is always reborn through various means after death, whereas Larfleeze is a living Power Battery who can't die from normal physical methods)

Both are formidable combatants in their own right, but often leave their fighting to their armies that follow their every command (Annihilation Wave for Annihilus and Orange Lantern Energy Avatars for Larfleeze)

Both suffer from immense paranoia which often becomes their undoing in most conflicts despite their immense power and general ability to think logically and strategically when they try

Both also constantly find themselves at odds with an intergalactic military/law enforcement organization (The Nova Corps and the Green Lantern Corps respectively) and are classified as universal threats