tournament_contest_versus_battle_effect

tournament_contest_versus_battle_effect = {
	save_temporary_scope_value_as = {
		name = choose_winner
		value = $CHOOSE_WINNER$
	}
	save_temporary_scope_value_as = {
		name = injury_chance
		value = $INJURY_CHANCE$
	}
	set_variable = {
		name = progress_to_victory
		value = progress_to_victory_active_contestant_value
	}
	var:next_versus_match = {
		save_scope_as = next_versus_match
		if = {
			limit = { is_alive = yes }
			set_variable = {
				name = progress_to_victory
				value = progress_to_victory_active_contestant_value
			}
		}
	}
	# Determine winner
	if = {
		limit = { scope:choose_winner = yes }
		random_list = {
			# ROOT WINS
			10 = {
				trigger = {
					is_alive = yes
					save_temporary_scope_as = versus_matchee_temp
				}
				desc = tournament_contest_versus_battle_win_tt
				modifier = {
					exists = var:progress_to_victory_score
					add = var:progress_to_victory_score
				}
				modifier = {
					exists = var:contest_aptitude
					add = {
						value = var:contest_aptitude
						divide = 2
					}
				}
				# Prefer unmatched rivals of players to not get knocked out
				modifier = {
					is_ai = yes
					scope:next_versus_match = { is_ai = yes }
					scope:activity = {
						any_guest_subset = {
							name = contestant
							exists = var:progress_to_victory
							this != scope:next_versus_match
							is_ai = no
							has_any_bad_relationship_with_character_trigger = { CHARACTER = root }
						}
					}
					factor = 2
				}
				modifier = {
					has_variable = murder_sabotage_target
					factor = 0.5
				}
				# If aptitude is higher, more likely to win
				modifier = {
					exists = var:contest_aptitude
					exists = scope:next_versus_match.var:contest_aptitude
					var:contest_aptitude > scope:next_versus_match.var:contest_aptitude
					factor = 2
				}
				# If have at least double aptitude of other character, you win
				modifier = {
					exists = var:contest_aptitude
					exists = scope:next_versus_match.var:contest_aptitude
					contest_aptitude_fetch_half_value >= scope:next_versus_match.var:contest_aptitude
					add = 1000
				}
				show_chance = no
                versus_contest_round_outcome_tooltip_effect = {
					WINNER = root
					LOSER = scope:next_versus_match
				}
				save_scope_as = contest_winner
				scope:next_versus_match = { save_scope_as = contest_loser }
			}
			# VERSUS CONTESTANT WINS
			10 = {
				desc = tournament_contest_versus_battle_lose_tt
				trigger = {
					scope:next_versus_match = { is_alive = yes }
				}
				modifier = {
					exists = scope:next_versus_match.var:progress_to_victory_score
					add = scope:next_versus_match.var:progress_to_victory_score
				}
				modifier = {
					exists = scope:next_versus_match.var:contest_aptitude
					add = {
						value = scope:next_versus_match.var:contest_aptitude
						divide = 2
					}
				}
				# Prefer unmatched rivals of players to not get knocked out
				modifier = {
					is_ai = yes
					scope:next_versus_match = { is_ai = yes }
					scope:activity = {
						any_guest_subset = {
							name = contestant
							exists = var:progress_to_victory
							this != root
							is_ai = no
							has_any_bad_relationship_with_character_trigger = { CHARACTER = scope:next_versus_match }
						}
					}
					factor = 2
				}
				modifier = {
					scope:next_versus_match = { has_variable = murder_sabotage_target }

As written in game/common/scripted_effects/04_dlc_ep2_tournament_effects.txt.