Im not aware of any card that provided 50 MQM on sign up.
There are cards where you can end up with enough MQM given the MQM you will get from your remaning 25 segments that you could make DM, if you can spend BIG enough before EOY. Check Delta reserve offers for business and personal.
A couple of mileage runs might be part of the solution.
I have to ask because I'm curious With so many segments, why do you want DM????