Ventrac with duals on it might handle the slope depending on what type of ground you are running on. That's a steep slope. Where are you finding that kind of slope? Retention ponds, highway off ramps, where. With more details folks here can give you more feedback. Pictures would also be helpful.
Whatever you are running your biggest issue will be keeping the engine oil running right with that much slope. Doesn't matter if it is a walk behind or a rider. Heck, we even toyed with the idea of putting a Rotex 2-cycle in a worn out Bobcat MT-52 just so we could go up and down the slopes.
Bottom line is that you need to give us more information.
If there is time to do it over there was time to do it right!