The bare minimum corrective action when you see "value added offers" in a Windows installer is to cancel the installation and then revert to the most recent restore point. There's no reason to assume the installer will honor your "no thanks" (as it often won't) or that it hasn't already taken the opportunity to hose your system (less likely but a definite possibility with the type of person who is willing to bundle malicious garbage in their installers for a buck).

You're thinking entirely the wrong way about that "type of person". Very few people think of themselves as evil; rather they will have some rationale for how what they're doing is OK, and very different from behaviour that from the outside seems to be the same thing. They will use any number of dark patterns to get you to misclick, but I've literally never seen such an installer not honour the "no thanks" if you can find it.

I was being a bit hyperbolic, but only a bit. I really don't trust someone who is willing to bundle up crap that obviously nobody wants, just to earn a few bucks when someone is tricked into installing it, but I can agree that it's a significant step from that to actually producing malware.

Most reports of "no thanks" failing to work are probably due to third-party installers from who-knows-where, but I've seen at least a couple of cases (PSPad and CamStudio IIRC, could be mistaken) where it was attributed to a bug in the official bundle.