Is everything bound by gravitational pull?

Everything is bound together by gravity, however since gravity is the weakest fundamental force and the strength of gravity decreases fourfold when the distance is doubled it's effect is often negligible. Light is also effected by gravity since light acts as both a particle and a wave, the collision you are referring to is the Milky Way-Andromeda galaxies collision. There is no known focal point or center of the Universe. Objects that achieve escape velocity can escape the gravitational pull of large objects and it would seem like it is free of it's gravitational pull but it is not and in fact it slowly slows down the object that achieved escape velocity just not enough to stop it from ultimately escaping.