If I repeated Frigid Touch a 2 might unit, does it go to -2 might?

Yes, if you repeat Frigid Touch on a 2 Might unit, its Might will become -2 for the turn.

According to RiftJudge FAQ #421, units can have negative Might values. While the game treats negative Might as 0 for purposes like combat or checking for lethal damage, the actual negative value is tracked internally for arithmetic operations.

Here is the breakdown of your scenario:

1. Initial State: The unit has 2 Might.
2. First Frigid Touch: Applies -2 Might. Calculation: 2 - 2 = 0 Might.
3. Repeat Frigid Touch: Applies another -2 Might. Calculation: 0 - 2 = -2 Might.

The unit's Might is now -2 (though it will be treated as 0 for game purposes). If you were to later apply a buff that increases its Might, that buff would be added to the -2 value.