Perhaps unpopular opinion: it sounds like the senior SDE isn't working out. Being non-condescending to other team members is a core part of the job. It shouldn't be persisting after you tell them that it's a problem that's causing serious conflict within the team.
There's a lot of previous discussion you could look up about whether to tolerate "brilliant jerks" on your team. My take is we usually overestimate how brilliant they are and underestimate how toxic it is to have a jerk around.
There's a lot of previous discussion you could look up about whether to tolerate "brilliant jerks" on your team. My take is we usually overestimate how brilliant they are and underestimate how toxic it is to have a jerk around.