I was eating my breakfast one day One day when I was eating my breakfast One day, (when) I was eating my breakfast a stranger比one stranger要好一些 came to punch没错,不过估计你要表达的意思是came and punched
One day I was eating my breakfast, one stranger came to punch my face 多谓语了,要改成并列句或复合句。比较常见的说法是 One day I was eating my breakfast, when one stranger came to punch my face. 另外,came to punch 语法上没问题,表意上似乎不如 came and punched。