Give back his pension

You raise an interesting question. Property division issues are "final" when you are divorced. I am not sure in my 34 plus years of practice I have ever had anyone ask to give back property that they were awarded from when they were divorced. Since we are uniquely dealing with a pension (defined benefit plan), the answer to your question may be where you currently are with receiving the benefits. If you were awarded a portion of the pension, and your ex has yet to reach normal retirement age where you can draw on his pension, and assuming further, no qualified domestic relations order (QDRO) was drafted and filed, it may be possible for you and your ex to enter into a post divorce stipulation and order to waive your interest in the pension and file it with the court for approval. If on the other hand, the qualified domestic relations order was completed and filed with the court and the  plan administrator, it may be now impossible to reverse that QDRO and have it undone. I am honestly not sure if it can be reversed without checking with an expert who is experienced in drafting QDROs and dealing with employee benefits. If the QDRO is properly done and filed and your ex is plan in pay status, or he is retirement age and continues to work, but you are already drawing your share of the pension, your other option is simply to pay him back the money each monnth as you receive it. That is a bit more tedious than undoing the orders and never receiving the benefit in the first place, but it could certainly be done that way. I would also suggest to you that you critically think through your decision.  The marital estate was to have been divided 50/50. I am curious why you only received 25% instead of 50% and you offer no explanation for that in your post. Before you decide to give back what is already yours, because either you don't finanically need it, or maybe feeling sorry for your ex, a lot of things could happen down the road where you may regret the decision. I don't want to burst your bubble, but your new marriage could result in a divorce, or worse, what happens if your new husband dies and you are on your own. At that point, you might really need that 25% pension benefit each month. Give it some very careful thought.