[exaldb]

I’ve been in this situation when I was a junior engineer and found it really frustrating. I’d literally done more work in a week than the “senior” had done in their time at the company. They had shipped one change (a migration) and then nothing for 8 months.

Why should I stay at your company as a junior engineer if the people I’m teaching things to are senior to me?

It devalues seniority and the general appearance of meritocracy in your organization to keep this person at senior. If you really want to be nice, give them the title and compensation that is appropriate for them. If you can’t do that, the right thing to do is to politely say it’s not a great fit for the role and let them go.