I use FXOpen with the highest leverage of 1:500, the broker has experience of 16 years in the financial market and is regulated in ASIC, Cysec, and FCA, so far so good, withdrawal process smoothly, and good trading conditions.
Some high leverage brokers that I know are fxview and hotforex. Both offer leverage upto 500x. Though commissions are a little higher with the latter one.
I have an account with Coinexx and they offer maximum leverage upto 500X. It’s enough for me as I really don’t have the guts to take very high risk and see my account going down in flames.