Divorce is probably indeed the word closest in meaning to what you want, although depending on context there is no benefit to any or either party built into the word. Contrary to what you postulated, there is no restriction on the quantity of entities involved in the use of divorce. One can even be divorced from things (usually elements of one's self, e.g., ideals, conscience, past). Disbandment, dissolution, and disassociation are similar, but to a greater degree have no implied benefit to any party.
One can be absolved or delivered from something, with an implied benefit, but these typically have a religious connotation (i.e. absolved/delivered from all your sins) and imply a greater benefit to the person receiving the absolution or deliverance.
In law, separation has a deeper meaning than in everyday English. It intimates that both parties are amicable to permanent separation, but that a divorce is not desired. In fact, divorce in this context has an obviously negative connotation. However, it is not simple to conjure this meaning of separation outside of that very specific context.
If you have a specific context in mind, it might make it easier to pinpoint the 'right' word.