The alien Symbiotes of the Marvel Universe have yet to show up in the MCU, but they're still as popular as ever in the comics, so it's probably only a matter of time.
ComiXology are currently hosting a huge sale on comics featuring the anti-hero Venom and his pure evil psychotic counterpart, Carnage. Lasting until November 27, it includes series including Venom: Space Knight, Venom vs. Carnage, Deadpool vs. Carnage, and the currently ongoing horror series simply titled Carnage, in which the titular serial killer takes centre stage. Although it isn't features in the sale, a new ongoing Venom series has also just been launched, which you can check out here.
By the way, Venom: Space Knight really is as awesome as it sounds.