You can almost say you already are halfay in his shoes, in a sense. The man lost a part of his family supposedly due to a murder culprit linked closely to MC. And now MC is in a position themselves where they lost family due to him murdering them.
But there are two possibly big key differences to situation between him and MC. The most notable one being what choice each readers' MC will make when dealing with Luceris: will they continue the cycle the king started or break it in some manner (not exactly forgiveness; just not resorting to his methods). The second (debatable) key difference is...well, MC saw for themselves Luceris had killed their family; was physically there when their home was under attack by him. Luceris, however, only discovered the poison when his wife passed away and has three big evidence that he claims as three big truths. However, while the clues may lead to the direction he and many others are convinced leads to the culprit being no question, they may not be as reliable as many believe. And MC themselves may discover something off if they look closer to things most others (maybe even the king himself) might've just did a glance of.