Gorilla

Nope. As far as I know, most Bigfoot/Sasquatch/Yeti sightings are well away from the range of the gorillas.

(For example: Does the gorilla face other predators attacking it, or is it’s enviroment becoming too polluted, or overpopulated by other gorillas. Does it have to compete with other predators for its food? Does it face deforestation?)
Human predation and habitat loss is taking its toll.
http://animals.nationalgeographic.com/animals/mammals/mountain-gorilla/
http://ngm.nationalgeographic.com/2008/07/virunga/jenkins-text
http://ngm.nationalgeographic.com/2008/07/virunga/stirton-photography
Just plain sad that we are so foolish and unable to [...]

The muscles in both species work differently. Squatting? Benching? Deadlift? Push? Pull? Hold things up for a long time or just for a second?
You can’t just make a blanket statement like that and assume a gorilla can throw a car just because it’s 7 times stronger than a man in one way

im going with the tiger!
Well it depends on the size of the animals involved. Adult male tigers range in size from 200 to over 600 pounds, depending on the species. Adult male gorillas are around 300 to 400 pounds. So a large gorilla could probably kill a small tiger. But if [...]

This atheist says yes. Protect our forest brothers. What do you say?
i think so
there’s only 200 probably because of human influence, so we have to help the remaining population.
we can’t just leave it to "natural selection". it would be like leaving bald eagles to natural selection after years of hunting to near extinction

On a level flat surface let’s say a field.
The bear is bigger, stronger and has more weapons in the form of claws. It has a longer reach than the gorilla and could land a major blow before the gorilla got close enough.
A big gorilla weighs 200kg and stands about 2metres. A big grizzly weighs 600kg+ [...]

Life has handed me lemons and I’m trying to make lemonade.
You Tarzan, me Jane.

a silverback in his prime would be overpowered and pinned by how many martial art experts?
It should only take one.
One that is smart enough not to fight any gorilla and that one must use some type of tranquillizing darts.
Martial Arts is not about being the best or strongest fighter. It is more about being the [...]

I want to have silverback as shown in the link below –
http://www.chambersburgscion.com/images/Picture/2007/December/lg_Male_silverback_Gorilla.jpg
I will get it when he is new born. That way he will be used to humans and will develop a bond. Gorillas are very peaceful, relaxed and calm animals. They are vegetarians. And i have a big back yard with lots of grass [...]

a Gigantopithecus was a type of gorilla that stood 9.8ft tall and weighed 1200lbs here is a link http://en.wikipedia.org/wiki/Gigantopithecus ]
and could it kill a modern day silverback or siberian tiger?
they were probably more like a type of orangutan than a type of gorilla. Orangutans are very strong.