In the future, Magical Dueling has become a big thing where millions of dollars can be earned and lost. In these tournaments, players face off against each other in 1 vs 1s where they take turns "summoning" magical dragons, warriors, and spellcasters to fight against each other. You can think of it as a variation of Yugioh/Magic/Pokemon TCG except with advanced magical battle technology.
You are one of the world's best Magical Duelists.
You participate in a World Cup with elimination rounds taking place in various European cities. This is the most high stake incarnation of this tournament ever. The final winner of the World Cup will not only be immortalised as a true master of Magical Dueling but will also become rich as a Lannister.
Every participant of the tournament must GAMBLE with 2/3 of all of their entire netsworth ("the entry fee"). The first prize winner gets ALL OF THE MONEY from all the participants' entry fee total (easily becoming a billionaire because of large player pool and the fact that many corporate-sponsored big names and career players are in). There is no other prize. If you lose, you walk away with 2/3 of all of your life's netsworth gone.
A win at all cost mentality is promoted. This game is considered by many to be too try hard (and borderline unethical) but nevertheless a high glory undertaking.
Cheating, hacking, and pulling strange unconventional stunts outside of physically assaulting/killing the other player is allowed (in fact, it is a tradition). Any attempts to grab, touch or hit the other player WILL cost the game though) In fact, the previous winner of the last tournament (not as high stake as this one) won the final game not in the mechanics of the duel itself but by hiring a gang of kidnappers to get to his final opponent's family and using this leverage to get his opponent to concede in the field. He returned to Helsinki where he was welcomed as a hero and the Finnish government refused to extradite him to Bulgaria; the Judges were impressed by this stunt and made him the World Champion. Under pressure from the corrupt UN, all charges against him were ultimately dropped.
You really really want to win this year's tournament and get billions of dollars.
In terms of your dream, you've always dreamed of becoming the Number One at this game.
You participate in the tournament and using your skill and knowledge of the game, defeat all of your opponents in elimination rounds in Berlin, Istanbul, and Vienna. You make it to the finals in Rome.
Your final opponent is a young French player called Emilia Leblanc.
The highly anticipated final 1 vs 1 is televised all over the world and takes place on a large floating platform high above the ground in the middle of the Italian capital. The winner will become a billionaire and also immortalised as the world's most skilled Magical Duelist (Number One).
The two of you battle it out, going in 100%. Both of you take turns summoning and commanding dragons, warriors, and spellcasters. Extremely elaborate mind games are played against each other and both of you are highly skilled in exploiting the weaknesses of each other's strategies. The game is extremely close as it gets to the end.
Leblanc is one turn away from completing a Magical Temple in the middle battlefield; if the Temple is completely built, you lose the game.
On your turn, you find a weakness of this strategy, defuse a major magical defence, and plan on telling your Wizard to blast the temple away with a powerful spell. It becomes clear that you are on the verge of winning and Leblanc can do nothing to stop this.
Before you order the Wizard to attack and win, you notice Leblanc walking to the very edge of the platform.
"WHAT THE HELL ARE YOU DOING?!" you scream out at her.
Leblanc: "If you tell your Wizard to attack, you Win. However, the impact of the force of the attack and the destruction of the Temple will cause me to fall from this platform. Its up to you."
"ARE YOU OUT OF YOUR MIND???????"
Leblanc: "I have come too far to back down now. Either I walk away the champion, or I walk away dead. That's how much I am determined to win. You can win, but you'll have to kill or injure me. Are you willing to do what it takes to win?"
"... ..."
You look around and analyse the situation:
1. The timer for your turn is coming up (30 seconds in fact)... if you don't attack and 30 seconds are up, it will be Leblanc's turn and she will win.
2. The Judges aren't intervening. This sort of stunt is what gets them high viewership and makes the game "alive."
3. There is no time or way you could hack or cheat to win at this point without destroying the Temple. If you destroy the Temple, there is 100% certainty that a shockwave will send someone standing on the very edge to fall.
4. The floating platform you are both on is about five stories high from ground level. If Leblanc falls, there's a substantial to high chance that she will die. There's also a chance that she'll only get injured but probably permanently crippled but the fatality rate is pretty high.
5. You do not have any magical capabilities that could work to rectify the situation at the time.
Your 30 seconds are coming up and you see that she's dead serious. What do you do? What is your justification?
Are you willing to do what it takes to win? Why or why not? Remember why you entered this tournament (see above)
Assume that there will be no legal consequences if you choose to attack regardless of what happens to her (although it will be the first time this has happened in the history of Magic Dueling). However, you will personally have to "live with" your decision to attack.
Due to the complexity of this hypothetical, the OP may edit with powers of clarification.