inhospitable, disassociative, discontinuous, disciplinarian, discerning (too short and you probably know all these, anyway), but onward: discretionary, disparaging, disencumbered, disenfranchised, disestablished, transubstantiate, act transmutably, transmogrify (is a bit fantastic), transitionary, inexorable, unrelenting, unmitigated and etc. because…

to tell you the truth, I’m not at all sure why I’m knocking my head against the brick wall of ideas and dictionary perusing when someone has undoubtedly given you a list a mile long from an instant source right there to copy and paste. Gets me every time!

intransigent

inexorable

implacable

obdurate

indefatigable

pertinacious

I haven’t looked them up in the dictionary yet so don’t know if they are all suitable.