Retro
The prefix "in" could be used with the word "vincible" to make it "invincible."
inter-
semi-
counter-
In
Prefix could be:MetaAltiMegaNeo
The prefix could be semi-, hemi-, or demi- , as all are used in English.
The prefix "in" could be used to make the opposite word insufficient.
Yes, "un-" can be added as a prefix to "blind" to create "unblind," which means to restore sight or remove blindness. However, it is not commonly used and "blind" is generally used without a prefix.
Centi... Deci... Suck-O-...
Trans is probably the most obvious
The abbreviation 'f' is also used for frequency which could cause errors