Brainiac
Super Freak
PAK doesn't even use a specific scale, and I think that's where the real problem is. But, yeah, they should definitely keep consistent sizes with characters that belong to the same franchise. It's really noticeable, for example, where GZ Big Boss is much taller than the Peace Walker figures.
That sucks, I'm currently getting the DC Variant figures, they seem to be consistent but I don't have them all yet