Gol-Qayin

The Disgraced Guardian of the Second Gate; Gol-Qayin is one of the Blazing Mountains Colossal Titans you'll come across in Titan Souls.

Tips for Beating
You'll need to shoot the Gol-Qayin in the back, and if you wait until he's spinning you can unlock an achievement. Time your Arrow perfectly and it won't be so hard.

An easy but dangerous way to win is to, immediately after his first attack, roll towards him and in the direction corresponding to which side he attacked with (roll right for his right ball, left for his left ball). If you repeat this three times, rolling in the same direction, he should start spinning. While he's spinning run and roll in a four-fifths circle around him in a clockwise direction. This almost always positions you close enough to his weak point that you can kill him immediately.