Resubmitted: can someone loose a healthy adjacent tooth if a newly placed implant next to it does not take and implant needs removal?

Technically yes..: .. But unlikely. There would have to be a major infection with major bone loss around that implant. So much so that the bone on that adjacent tooth was compromised. That scenario is very unlikely.. The implant would be removed or expelled long before this happens.

Failing implant: Not in the short term, and only over a long period of time if the dental implant fixture was close to the adjacent natural tooth and the bone around the failing dental implant continued to deteriorate and became infected. What you describe is very unlikely to cause any damage to the adjacent natural tooth.