Those jaggies you see on some of the letters was always there, they were even more noticable in the old script, wasn't the subs in g-force's original script located in the black bars? If so, they don't have that problem.

Both, Moth3r and satanika above have been very helpful with suggestions, but unfortunately I don't think I'll be able to fix that issue in the limited time frame or if their suggestions even solve those jaggies entirely, I've not had the time to look into it. I actually tested to put the subs before the anti-aliasing part, but they were still not completely gone with that method so I don't know if it is a limitation in the Avisynth subtitle filter or if it is a limitation of my knowledge, as it is now it doesn't have any halo color, but if I put that back, it doesn't resemble the theatrical subs anymore so...