The giant may hit hard, but his attacks are very sluggish. Simply dodging his attacks then attacking nonstop is the simple and easy method. The only real danger is his stomp which is an unblockable AOE attack. If you can dodge that, you'll easily take down the giant. As the giant isn't weak to water however, you can also Armatize with Mikleo and merely attack from afar. Either strategy works very well.