Radical Candor is Caring Personally while Challenging Directly. At its core it is guidance and feedback that is both kind and clear whilst specific and sincere.
What it is not...
This is 'brutal honesty' - challenging but not caring
This is what happens when you want to spare someone’s short-term feelings, so you don’t tell them something they need to know. You Care Personally, but fail to Challenge Directly.
This is backstabbing, political or passive-aggressive behaviour. It is what happens when you neither Care Personally nor Challenge Directly and being 'Two faced'. Should you be a leader if you genuinely feel like this?