2 best ways to tame it by my perspectives are: get a super high level equus with good mutations, good saddle, health and attack. By this the Giga wouldn't be able to kill u quick but your equus can knock it out with really low kicks quickly. Remember to add speed levels in the equus because gigas are quick.

The other way is to tame up a high level basilisk with a high level saddle. Then from a hill or mountain, try to knock it out by the toxic balls. Remember to pump in some speed to catch up with the fleeing Giga.

Really helps :)

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