Master Q is correct. First strike allows the character with first strike to apply his strength (*/) prior to the opposing character during battle resolution. So in a mutual destruction situation the first strike character wins. However that does not take into account other abilities that can be applied, such as immunity, ignore and protection. If one character is protected from another, first strike won't matter because you're not allowed to harm the protected character. First strike is not a type of immunity that keeps the opposing character from harming the first strike character.