This discussion is becoming cyclical. Why don't we address one problem at a time?

The gigantic mech weighs fuckall, it should be able to lift fuckall. This incredible strength is offset by its entire body being a weakspot. 
Trip it, and it will take forever to get back up. 
Climb up its back and it will wind up destroying itself trying to get to you.
Crawl into its enormous hands and work your way inside of its body. 
Jump into the cockpit and the guy inside is only low tier.
Stuff its mouth with explosives. 
The list goes on.

While its offensive capabilities are impressive, and its defensive capabilities seem so as well. It's actually quite defenseless if you can get close enough to it.

Sever the wrong wire in its torso and hell, the thing will be crippled. It's obviously hollow, otherwise it would weigh several hundred more tons.