system
Given the following post, respond as if you're commenting on Reddit:
human
[Resident Evil] How cost effective are Umbrella's bioweapons in the first place?

Manipulating biological contaminants like the T and G viruses probably costs enough to outfit a Delta Force team. Given the end products, just how cost-effective are these monstrosities when used against trained military forces?
gpt
Not very effective, it turns out. Or very effective, depending on how you look at these things. An uncontrolled T-Virus outbreak completely destroyed Raccoon City; it was so bad a nuke was required to contain it. If you WANT to do that sort of thing to the enemy then yeah, it worked pretty well. No loss of life for your soldiers, and an immensely scary display of power for yourself.

The problem is that the whole point of warfare is, when you are fighting for something, you generally want to be able to use it afterwards. Which isn't easy when the entire thing is covered in zombies and monsters. While T-Virus is great for killing off civilians and enemy combatants the bad news is that the same thing that makes it dangerous to them also makes it dangerous to the people you send it to occupy it. It's a double edged sword, most of the creatures don't follow orders and will attack you as easily as the enemy.

Umbrella was experimenting with creatures that could follow orders. The Nemesis was basically a Tyrant with some very low-level mental conditioning to hunt specific targets. However, it wasn't perfect. Nemesis wasn't intelligent enough to distinguish friend from foe and couldn't do anything more intelligent than blindly pursue targets. 

In short, the T-Virus creations have a high success rate against most military and civilian targets, especially those without prior experience or training in combating them. However, like most biological weapons they are uncontrollable and the clean up is a bitch.