I adopted two for my first time years ago...
One was very small and blonde, maybe 30 days max.
The other was large and older, about 6 months.
I played with both equally but the little blonde day by day became more and more aggressive! Untill evetually removing food or refilling the water bottle became a problem. He was healthy, just mean. The older one was always calm and would never bite.
Its kinda of risky, but I do it because it works for me....
While the hammy is somewhere hiding, I put a loosely balled fist into the center of the cage. If it doesn't wake them you can make some noise to attract them. If you see your hamster silently charge out of its (very rare unless you put another hamster in the territory or the hamster is extremely aggressive) id would remove your hand. LOL.
But if they come up normally, dont flinch! If you feel scraps of teeth, just remember its ok, they just want to know what you are.
I have a little boy named Alexander who I THOUGHT was a biter.
Until i tried this with him (i was hesitant to) and it ends out all he wants is to gently nibble all day long. XD