When seeing a giga, run. If you intend to tame, bring BULLETS, and FRIENDS they are not a fun tame to knock out or feed. They are stupid and have low agro so lead it by something if you're being chased. Don't let them RAGE it is bad, they throw you off, murder you and then eat you. Raging happens when they take about 1000 hp of damage.
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.
I spent an hour taming a Max lvl anky on a ledge. After about 20 minutes I looked down and 2 gigas were below looking right at me their heads almost reaching the top of the ledge. They stayed there the entire time