Venom is respected for it's character development, plot and action. Let's just focus on that action for now. Throughout the series, Flash Thompson is involved in a number of battles against a variety of different villains (and sometimes heroes) and I've tried to narrow this down to my top few favourites.
Vs. Kraven (#2)
Venom's first battle against a long-time villain of Spiderman happened in #2 of his series and involved spears, tranq darts and dinosaurs. He has come across Kraven the Hunter in the Savage Land who wants to kill Flash, believing that "the Spider's black spirit" would bring him peace. Throughout the battle, you really get the sense that Flash is a newbie hear and is filled with panic and almost terror while close-ups of Sergei's face capture his madness well.
Vs. Ant-Venom (#7)
Occurring during the Spider-Island story arc, Venom is tasked with bringing in Eddie Brock who has the ability to turn people back into normal humans after being mutated into spider-like creatures. This is no easy task and Flash barley makes it out of the fight conscious. The action is done very well, seeing both of the symbiotes punch and claw each other is entertaining and their attacks are almost bestial in nature.
Vs. Jack O'Lantern (#12)
Although he's fought his arch-nemesis a number of times previously, this is the battle that stands out between Flash and Jack O'Lantern for me. Although calling it a battle might not be quite accurate, the encounter mainly involves Jack trying to escape from Venom who, for the first time, has fully embraced his anger and "vulked out" into a mad behemoth. Seeing this for the first time is something that I remember thinking was really cool and the design of Flash's suit while in this state has been well-thought.
Vs. U-Foes (#28)
Flash is out of his weight-class here and he knows it, he admits that even when he fought these guys in the past and had back-up they nearly killed him. By no means does that stop this clash from being riveting though and for a moment it almost seems as if Venom has a chance at beating the U-Foes. Almost. In the end, as you can probably guess, our hero ends up being almost being killed but the fact that he's able to go head-to-head with these villains shows how far he's come in terms of his level of control over the symbiote.
Vs. Toxin (#34)
Eddie Brock makes this list a second time and deservingly. After having the Anti-Venom symbiote taken away from him, he's forcefully bonded with Toxin who, for those who don't know, is the spawn of Carnage. As you can imagine, the spawn of Carnage is going to be pretty powerful and this time, unlike in earlier issues where the two encountered, Flash is without any sonics so how will he defeat Toxin this time? Well, if you know then good for you, if not...then WHY? Go and read this thing!