I would like to ask on behalf of my brother, he had an arranged marriage in Pakistan, he had called his wife over to the UK but has never loved her or wanted to be with her, he was only with her for the sake of parents, but then he got locked up dor money laundering he got a 3 year sentence to which he does 1 and half years, when he got locked up his wife started doing all the things that were least expected of her and causing his family bother now that he is locked he wants to know if he can send her back and what is the best way from prison

A wife isn't something you "send back". I understand this was an arranged marriage. But I assume it was an religious one. Therefore its subject to both civil and religious rules on the dissolution of a marriage.

Your brother can consult a divorce solicitor (even from prison) who can advise on how he can dissolve the marriage. From there, you would need to check with UK Immigration on her status after the divorce.

I just wanted to say that if your sister-in-law partook in an arranged marriage, and then her husband was sent to prison, it is she that got the raw end of the deal. If your family is worried about their reputation, then perhaps they should look to your brother before scapegoating this woman. She has uprooted her whole life, left her family and friends and all that she values in hope of a good marriage and better life, and she ends up alone in a foreign land with, clearly, unsupportive in laws...
Quite frankly, if you want to be 'send[ing someone] back', then I don't think she is where you should start.

If this women is his wife there is nothing he could do about the situation... especially since he is now a felon in the system... it is up to woman if she desires to re-enter her home land... sorry there is a culture difference here in the west... women have the right to choose their destination... if your brother desires a divorce from this woman then he can do so behind bars... and even with a divorce she can ask to stay...