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Are these all correct and natural?

Whatever he's done to your son he must have deserved it.

Whatever he did to your son he must have deserved it.

Whatever it is he's done to your son he must have deserved it.

Whatever it is he did to your son he must have deserved it.

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Are these all correct and natural? Yes, except that I'd add a comma to each, as shown.

Whatever he's done to your son, he must have deserved it.

Whatever he did to your son, he must have deserved it.

Whatever it is he's done to your son, he must have deserved it.

Whatever it is he did to your son, he must have deserved it.

Comments  
anonymousAre these all correct and natural?

Yes, but I would put a comma after "son".

 Clive's reply was promoted to an answer.