Can a shareholder who wasn't oppressed still benefit from someone else's oppression claim?

Generally, the oppression remedy is meant to address harm to the specific complainant who brings the claim, so relief is usually tailored to that person's situation — a share buyout ordered for the complainant, for example, is generally about that shareholder's shares and interests, not automatically extended to other shareholders who were not part of the claim.

That said, some remedies a court orders can have effects that reach beyond the individual complainant. If a court sets aside or varies a corporate transaction or resolution because it was found oppressive, undoing that action can restore the corporation, and by extension all its shareholders, to the position it was in before, which may incidentally benefit shareholders who were not part of the oppression claim at all. Similarly, if the remedy involves removing a director or reforming how the company is governed going forward, all shareholders may benefit from improved governance even though only one shareholder brought the claim. Whether a particular remedy has this kind of broader effect depends entirely on what the court actually orders and the nature of the underlying conduct — a personal buyout remedy is narrow, while a remedy that restructures the corporation itself tends to be wider in effect.