When a sentence ends with '来了', is it the aspectual or modal particle 了? I understand the differences between aspectual and modal particle, but I have some confusion about when a sentence ends with a 了 and at the same time with a verb, like 来了. So it is aspectual or modal?
“来” is an action. So it is aspectual. It indicates the action has ended.

“来” is not a situation. Although a situation that "I am here" can be inferred from the fact that the action of coming (来) has ended. So it is not an indication of new situation.

You can say "我在了", in which the "了" is modal. "在" here indicates a (new) situation.