Once any transaction gets even 1 confirmation, it can't be reverted, double-spent or anything.
For the sake of completeness:
A transaction, theoretically, can be double spent after it already has been confirmed.
This, of course, needs quite a big % of the computing power of the network (PoW)
and a bit of luck (depending on the computing power) to success.
In an aimed attack its even possible to "sacrifice" 1 self-mined block to "fake" 1 confirmation of a TX. This can be made without the TX getting confirmed "on the real network".