This Colossus has a huge stone bar in place of a hand and can either slam it straight down or on an angle. Do not get hit, as it will take a remarkable amount of time to get up again. When he slams it down on an angle, it will stick in the ground for a few seconds. You can then jump onto it and run up to the Colossus' arm. While you can do this, it will not do much good as you cannot get past the armor. As you run around, you will notice a large, circular stone platform. Stand on it and let the Colossus try to hit you. Dodge, and it will smash down onto the platform. The armor on its arm will shatter, allowing you to climb up to its head and jam your sword in the sweet spot. After a few of hits, it will change and be on the Colossus' stomach.