I'm not going to bother with a bunch of research but:
Gunnar Henderson, 21, 259/348/440 126 OPS+
Ryan Mountcastle, 23, 333/386/492 137 OPS+
I don't think it's all that rare.
They could easily get away with holding grudges back in the day. Was basically no accountability. Just think how wild it was before the games were televised.