My mom got divorced, so I knew sthg.
There are few types:
1 - 通姦, but you really need to find pictures or videos that they were making love, naked in bed.
2 - 不合理行為, like he hits you, or does something very unbearable to hurt you (but physical injury or emotional disturbance). But the lawyer said, if you employed this reason, you have to find sme behaviors which happened for the recent 6 months. If you find the behaviors, which happened for few years, the judge will question you why you get divorce now, but not few years ago.
I am not a lawyer, all these were told by the one that handled my mom's case. I do rather suggest you to seek help from a lawyer.
Btw, divorce is a big decision. Please consider it carefully.