Henry VI was the king of England during the 15th century. If you're looking for synonyms to refer to him, you could use titles like "monarch," "ruler" or "sovereign." Other terms could include "king of England," "tyrant," or "leader of the House of Lancaster." You could also refer to him as the "third monarch of the House of Lancaster" or the "last ruler of the Plantagenet dynasty." Whatever term you choose, it's important to make sure that your readers understand exactly who you're talking about, especially if you're discussing Henry VI in the context of historical events.