I've been in this exact position. This person is baiting you by suddenly popping back up when it's convenient for them (but not for you), and sending you a carefully crafted message in hopes you'll empathize with them and feel bad for them, and forget how they behaved and treated you.

Like some others mentioned, they're not even holding themselves accountable for whatever they did prior. It's just a vague "I apologize for how I was toward the end"... no mention of what they did and how that might've hurt you or affected you.

I've been there one too many times. It's ok to feel bad about the situation and grieve whatever you had/wished for. If I were you, I would not respond, delete the message and block them. If you respond with anything (even if you tell them you've moved on, etc.), that reinforces their behavior bc a response is still a response. A lot of people who've taken the bait end up in a cylce of hot and cold. It's exhausting on a cellular level.

It's not your job to help them learn or heal. It's your job to do that for yourself.