Hey

Don't know if it is the same as Japanese, but 新手 is "new (opponent)"
大 is "large/great"
Don't know if it is 師 that is simplified, but that would be "mentor"
So something like "New Leader" perhaps? Sounds ego-inflated enough to be a screen name.

新しい (New in Japanese, though you probably know that)
I recognised the first three, but it’s interesting to see it’s more like opponent