+10% exp per kill. Works similar to the Credit Card, since it requires kills. This badge is extremely helpful if you want to level up fast. Offensive classes, or any classes that have strong firepower have most use from this item.
Most effective in games with lots of kills to win. You can make a custom match with lots of kills and camp, after you win your hero will level up very fast. Once you reach level 30 with the soldier who uses this, don't forget to remove it because it becomes useless.