Because of the fact that they're not limited by a special effects budget, we get to see firsthand just how powerful Immortals are supposed to be compared to mere mortals. They hit with the force of a wrecking ball and move with blinding speed and grace. When they attack and cut through their opponents, they move so quickly that they've become veritable human blenders. Immortals who are lucky enough to live for centuries, if not millennia, are beings of incredible power and influence, and this movie shows you just how many magnitudes they are in excess of regular human performance.
Pretty much anything Colin and Marcus does is automatically awesome.
Colin's first duel in the movie against an Immortal named Malike, who looks rather demonic and uses a massive chainsaw as his preferred weapon against other Immortals. To make it even more amazeballs crazy, Malike RIDES HIS CHAINSAW SWORD INTO BATTLE.
Colin surviving the explosion of his Spitfire over the German countryside and landing on Marcus' private plane. While surviving an explosion is cool and all, he used the explosion to propel him onto the wing of Marcus' private plane without a single scratch. Even Marcus was impressed by that one.
Colin ripping a parking meter out of the ground, with a large chunk of concrete attached to it, and flinging it hundreds of feet into the air at an outdoor TV screen, on which Marcus' face can be seen giving an announcement to the people of Manhattan.
Colin killing a massive mutant crocodile in the sewers of New York City. Totally unexpected, but freaking awesome.
Dahlia's Taking You with Me moment against Kyalia. Made especially cool by how the latter was bragging about everyone dying except for her and Marcus.