A situation like this can arise in a simple game such as checkers or chess, or it can apply to more complex scenarios like economic competition, academic mastery of a given field, or military might.
Note that merely being the strongest player is not enough for a handpalm scenario. The scenario must become so lopsided that no action by any of the opposing elements can possibly break the victor's dominant position, short of intentional self-handicap or monumentally inept play.
HMB: "I played chess against my girlfriend last night. It was brutal. She started with a handicap of one Bishop, one Knight, and one Rook and she STILL managed to corner me with two Queens and a Rook. She then spent ten moves of her stalemate count just taunting me with them to make her point."
HDT: "Wow. I've never seen a handpalm of that magnitude. Rusty?"
HMB: "You're telling me. I played a game of chess against myself the other day and somehow managed to lose."
HMB: "My girlfriend inflicted the most intense handpalm last night. I'm still staggering from the blow."
DTM (who doesn't understand the term): "NIIICE! High five?"
HMB: "...no. No, I think not..."