Holding a friend accountable is uncomfortable because you care. Indifferent people never bother.

The discomfort of saying something hard to a friend is not a sign you are overstepping, it is the cost of actually being invested. Indifference is frictionless, which is why people who do not care never have this conversation. Being told the truth by someone who has no reason to bother is rare enough that most people recognise it as care eventually.

Say it once, privately, and make it about the specific thing rather than a summary of them. Then keep being their friend regardless of how they take it. That second part is what proves the first was not an attack.