I'm afraid I haven't made my issue clear.
Setting the velocity negatively affects the gravity of only the specific game object. If I were to change the universal gravity to make the player work correctly, it would make everything else worse.
The issue is with how I'm using set velocity. Because the vector3 for movement has the Y value set to 0 by default, the object is not affected by gravity much, if at all. If the Y value is modified by including a downwards velocity, the player can not move outside of a small space.