OK, so Agony as a humanoid creature doesn't appear in Venom, but the symbiote does, as the unnamed blue extraterrestrial that Drake tries to bond to Isaac and one other vagrant before using it to execute Dr. Skirth (Jenny Slate) for her betrayal. The symbiote bears some resemblance to the Klyntar in the comics known as Agony.
Agony first appeared in Venom: Lethal Protector #4, like the other Life Foundation symbiotes. The original host was security guard named Leslie Gesneria, and as Agony, she possessed a couple of abilities unique among the five symbiotes. She could spit acid and absorb different chemicals to be used in a variety of ways. Obviously, we see none of that in the film, and because the symbiote seemingly perished along with Dr. Skirth, it's unlikely we'll see Agony return for a sequel.
Only the Phage symbiote seems to appear in the film. We see it early on, when Drake and Dr. Skirth experiment with live test subjects. They unleash the yellow-and-black Phage symbiote onto a rabbit, which is quickly consumed by the alien suit from the inside. The suit is seen completely destroyed later on, alongside a deceased vagrant, after being bombarded by intense sounds.
In the comics, Phage bonded with a security officer named Carl Mach. Along with the standard set of enhancements and abilities available to all symbiote hosts, Phage could form powerful weapons with his suit, much like the ones Carlton Drake uses as Riot. We don't get to see that in Venom because, as we've mentioned, it seemingly perished after Drake's experiments gave it too many incompatible hosts. Like Agony, it seems highly unlikely we'll see this symbiote again.
How can we list the film's symbiotes and not mention the star? Venom, of course, makes an explosive entrance after nearly two whole acts exploring a very human Eddie Brock, and a fight and chase sequence filled with teases The two have a complicated relationship, as one would expect. They don't agree with each other, but they need each other to survive the ordeal they've found themselves in.
The film draws story elements from the Venom of Marvel Comics' primary continuity, well as the Ultimate Universe, in order to recreate a dualistic creature that has no connections to Spider-Man. In the comics, Eddie was a struggling journalist who lost everything after making a mistake while chasing a story. He blamed Spider-Man for his downfall, and that hate was what drew the symbiote. Eventually, they give up on their search for revenge and move to San Francisco to become its lethal protector. There are more than a few similarities between the comics and the film adaptation, although they don't always appear in the way you'd expect. Whether that actually works is up to you to decide.
In theaters nationwide, director Ruben Fleischer’s Venom stars Tom Hardy, Michelle Williams, Riz Ahmed, Scott Haze, Reid Scott, Jenny Slate, Woody Harrelson, Sope Aluko, Scott Deckert, Marcella Bragio and Michelle Lee.