Don’t fight this thing head on.

To kill this thing without a (heavily mutated) giga of your own, you’ll need one of the following:

1. A ranged attacker such as a wyvern or velonasaur and a way to prevent the giga from reaching you.

2. A trap and some rather disposable allos and/or deinonychus.

3. A large gang of dinos bred for killing bosses, such as rexes.

4. Turret death wall

5. (Arguably easiest way) A large patch of water to lure it out to. Gigas never learned how to swim. Bonus points if you add sharks to make it bleed and die even faster.