Smurfing
Also said as Smurf, Alt account, Boosting (its cousin)
A skilled player on a new account, so they get matched with beginners. The system is doing exactly what it should, and it takes many one-sided games to find out.
New players meet the worst opponent possible at the worst time, and many of them leave. Punishing it is hard, because a new account with good results could just as well be a talented newcomer.
Say it
“Give new accounts a high K so a good player climbs in 10 games, not 60. Weigh performance as well as wins for the first 20 games, and do not rate accounts that have no verified phone number.”
Not to be confused with boosting
A smurf is a good player on a low account, for their own sake. Boosting is a good player on somebody else's account, to raise that person's rank.