Example:


Ixigia enters 4 games. His global chance (gc) is 0.73 (1*0.9*0.9*0.9)
Leo enters 3 games. His gc is 0.81 (1*0.9*0.9)
I entered all 5 games. My gc is at only 0.66 (1*0.9*0.9*0.9*0.9)
SpykeZ entered only 2 games. His gc is 0.9 (1*0.9)
Sabin entered 4 games just like ixi and has a gc of 0.73



Game: The Walking Dead Season 2
Contestors: ixigia, leo, pumpaction, spykez
Chances: 0.73<1.54<2.2<3.1

(^^ Chances: ixi's gc is .73, leos is .81, so ixi will win if the pulled number is between 0 and .73 and leo will win if the pulled number is between .73 and 1.54 (.73+.81) and so on.)

Pulled number: 1.515526295960957
Winner: LEO with a chance of 26.17%

(Leo won, even though his chances were a bit smaller than SpykeZ')
-----
Game: Crusader Kings II + DLC
Contestors: sabin, leo, pumpaction
Chances: 0.73<1.54<2.2
Pulled number: 0.020782751556434814
Winner: SABIN with a chance of 33.21%
(This time Leo lost, even though he had the greatest chances)
-----
Game: Ace of Spades
Contestors: ixigia, sabin
Chances: 0.73<1.46
Pulled number: 0.4630871486693599
Winner: IXIGIA with a chance of 50%
(Both entered 4 games, their chances were 50/50)
-----
Game: Saints Row IV: Century Edition
Contestors: pumpaction, spykez
Chances: 0.66<1.56
Pulled number: 0.8388793014799799
Winner: SPYKEZ with a chance of 57.84%
(Spykez wins clearly, as I entered every game and he had much higher chances to win this one)
-----
Game: Revenge of the Titans
Contestors: leo, sabin, ixigia, pumpaction
Chances: 0.81<1.54<2.27<2.92
Pulled number: 0.04176595187680257
Winner: LEO with a chance of 27.7%
(Out of all of us Leo had the highest chance to win, because he entered less games than the rest and he did)
-----
Game: Garry's Mod
Contestors: sabin, ixigia, pumpaction
Chances: 0.73<1.46<2.11
Pulled number: 0.033696457486511594
Winner: SABIN with a chance of 34.48%
(This time Sabin won, I clearly had no chance)


If one enters all 68 games, his gc is <0.1%

Repeating this script gave me good results and the 10% penalty per game entered, seems reasonable enough to prevent spammers from winning everything and doesn't hinder your chance just because you entered 5 games TOO much. If you think that 10% is too harsh, we can also try with a bit lower number...

Code:

function getWinner() {   Logger.clear();     var sheet = SpreadsheetApp.getActiveSheet();   var range = sheet.getDataRange();   var values = range.getValues();   var contenderMap = {};   // Get all contenders and calculate how many games they enter and their global chance   for (var i = 1; i < values.length; i++) {     var contendersTrimmed = values[i][3].trim();     if (contendersTrimmed != ''){       var contenders = contendersTrimmed.split(",");       contenders.forEach(function(contender){         var contenderTrimmed = contender.trim().toLowerCase();         if (contenderTrimmed != ''){           if (contenderMap[contenderTrimmed] == undefined)             contenderMap[contenderTrimmed] = {count:1, winchance:1};           else {             contenderMap[contenderTrimmed].count++;             contenderMap[contenderTrimmed].winchance*=.9;           }         }       });     }   } // for each game calculate the total chance (sum of the gc of each contender for this game)     for (var i = 1; i < values.length; i++) {     var contendersTrimmed = values[i][3].trim();     var totalChance = 0;     var possibleWinners = {};     if (contendersTrimmed != ''){       var contenders = contendersTrimmed.split(",");       contenders.forEach(function(contender){         var contenderTrimmed = contender.trim().toLowerCase();         if (contenderTrimmed != ''){           totalChance += contenderMap[contenderTrimmed].winchance;           possibleWinners[contenderTrimmed] = totalChance;         }       });             Logger.log("Game: " + values[i][0]);       Logger.log("Contestors: " + Object.keys(possibleWinners).join(", "));       var chances = "";       for (var possibleWinner in possibleWinners) {         chances += Math.round(possibleWinners[possibleWinner]*100)/100+"<";       }       chances = chances.substring(0,chances.length-1);       Logger.log("Chances: " + chances);         // pull a number which is 0<=x<totalChance       var winnerNumber = Math.random() * totalChance;       var winner = "";       var lastWinner = 0;       for (var possibleWinner in possibleWinners) {         if ((winnerNumber<possibleWinners[possibleWinner]) && (winnerNumber>lastWinner)){           lastWinner = possibleWinners[possibleWinner];           winner = possibleWinner;         }               }; //calculate the chance this player had to win this game against the other contenders            var luckperc = Math.round((contenderMap[winner].winchance/totalChance)*10000)/100;       Logger.log("Pulled number: " + winnerNumber);             winner = winner.toUpperCase() + " with a chance of " + luckperc +"%";             Logger.log("Winner: " + winner);       Logger.log("-----");       values[i][2] = winner;     }   } //update spreadsheet   range.setValues(values); //log who entered how many games and what their gc was   for (var key in contenderMap) {     Logger.log(key + ": " + contenderMap[key].count + ": " + Math.round(contenderMap[key].winchance*100)/100);   } };