This is by far the best animal in the game but at the same time you never and I mean never attack or try to attack another wild giga. The wild gigas no matter what level have thousands of more health and almost 3 times the amount of damage as a tamed giga. And even with multiple level 200+ gigas you would not even want to attack one level 10 giga as that the faster the wild giga goes into Rage Mode the faster and more likely you and your whole team of gigas are to die.
If one is encountered near water, you can simply lure it out to sea with a flyer and it will swiftly drown. Given the water is deep enough. If encountered inland not near water. Pray to the overseers you have something fast enough to out run it. Then promptly die because they're as fast as a mad Hispanic mother with a shoe. Not as deadly as one though.