A new Developer is having continuing conflicts with existing members or the scrum Team, which...

According to the Scrum Guide, the Scrum Team is responsible for removing a Developer from the Scrum Team if necessary, as they are self-managing and accountable for creating valuable Increments. The other options are not valid, as they imply that someone else outside the Scrum Team has the authority to remove a Developer (such as the Scrum Master, the Product Owner, or the hiring manager), which is not consistent with Scrum values and principles.