I heard that anti-particles annihilate when in contact with normal-particles but the odd thing is that in fusion reaction normal-particles often "fuse" into each other but the weak force often prevents it from happening so my question is how can anti-particles annihilate with each other for anti-particles from what I know (not much!) are affected by gravity as they fall downwards like like expected and their electrically behave same in sense that they attract with opposites and repel with other particles with same charge.
Now logic follows weak-force must also act as expected however clearly it annihilates so what force dictates that, I personally do not think it is the electrical forces as they are far from as strong as the weak force so what dictates this annihilation?
Is there a force? Is there a quantum effect? or what is it?