The GTVA Colossus was originally created to repulse a second Shivan invasion comparable to the first Shivan attack during the Great War. However, it turned out it did a great job handling the Neo Terran Front. However, when the Shivans attacked it was pushed back by the Sathanas, which may be seen as a failure.
The Colossus has many 'variants', as the default loadout for the Colossus concists of TerSlashes and BGreens, while the Colossus during High Noon is armed with LRBGreens and BFGreens (well sort of).
However, it should be noted that the Colossus was never made to battle ships of its own size, it was only designed to battle superdestroyer scale ships. It was seemingly capable of destroying smaller ships such as destroyers easily, which was what it was made for.
It could be said it also failed at fighting destroyers, evidenced by its battle against the SD Beast in Their Finest Hour, a mission which made many people doubt the Colossus. In that mission, it was disabled and damaged, meaning it was quite obviously at a disadvantage.
So, the Colossus, Terran juggernaut, hit or miss??