Hello tnvipdk1
I'm really sorry to see that you missed to evolve your Froakie, but sadly, we can't do anything for you about that.
There is no feature to lower a level on a Pokemon...
I can understand that is frustrating for you and you wasted your time, but again, there is nothing to do. :confused:
The only advise I could give you for the next time is to be more careful, and evolve your Pokemon around level 96 then use Rare Candies, just to be sure.
I wish you a nice day.
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