Your sentence is okay, but in natural speech we usually don't describe people as "regretful." Instead we use the verb form, and say that the person "regrets" something. If you've already explained what he did wrong, I think the most natural sentence would be: "He regretted it four months later." OR "Four months later, he regretted it." A couple of examples: "In March, I decided to buy a new car. I regretted it four months later, when I realized I couldn't afford the payments." "He broke up with her in a fit of anger. Four months later, he regretted it, but when he tried to call her, he found out that she had already found a new boyfriend."

I think the phrase that feels more natural depends on context of the conversation. To say, Four months later he was regretful sounds like something should follow it. It sounds to me like you would go on to explain why it took 4 months for him to feel regret. He felt regretful four months later, to me, sounds more like the end of a thought or point you're trying to make. But, if you were to write it in a book or a paper, I think "Four months later, he was regretful” would be more accurate.

thanks dear Angela 🌹🌹👍

به شما ربطی نداره Arasp. کسی از شما نپرسید.

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