With base 120 Defense and 150 Special Attack, it would fit your criteria. Base 90 speed also makes it possible for Dialga to be outsped by Magikarp (with IVs and Nature in effect), but isnt as slow a some of the next Pokemon.
Darmanitan (Zen Mode)
105 Defence and 140 Special Attack is pretty good for what you need. Its also really slow, at just 55 base Speed. The problem is that standard mode darmanitan doesnt match what you need at all.
Base 115 Defence and 130 Special Attack would also work for you. It only has base 60 Speed, which lets it become outsped by many. Also has unique typing.
It has base 110 Defence and 130 Special Attack, and just 65 Speed. HP stat could be better, though.
110 Defence and 100 Special Attack. Only 30 Speed, and also gets a Mega Evolution which boosts its Defence and Special Attack even more.
If none of these Pokemon work for you, I could probably find two or three more.