A level 28 giga spawned close to where I lived and I was really worried it would have destroyed all my games and everything I build. So like an idiot I took my quetzal, grappled it and drained 1000 bullets from my assault rifle into the giga only to take away half its health. But if you hurt it bad and it can’t reach you it will eventually run. Try to drive it out to sea and make sure it’s focused on you. It won’t realize that it’s health is being drained by megs and like that your house and tames are safe. PUT THIS UP SO EVERYBODY CAN SEE!!!
It's almost impossible to kill a level 20 wild giga with a perfect 150 tamed giga, you need to breed 2 high level giga's and have a strong saddle to even stand a chance if you're trying to kill a wild giga. Remember that every wild giga has 80,000 health points.