So I’ve always had this knowledge before but it just occurred to me that the first time Ron and Hermione truly saw Voldemort was when he walked into the Hogwarts courtyard with a dead Harry in Hagrid’s arms.
That was the first time they actually truly saw Voldemort.
Harry was alone went he went into the chamber in PS/SS.
He was (nearly) alone when he saw Tom in CS. I say nearly because Ginny was there but she was unconscious. Still, it’s entirely possible that she got a glimpse of him before he took her life away. A sort of Phantom of the Opera esque moment where he lured her down into the chamber and then she collapsed. But I digress.
He doesn’t appear at all in POA.
Harry’s the only (live) student in the graveyard in GOF.
They were not physically capable of being in the corridor to see him at the end of OOTP, no matter what the movies try to make you believe. (God the movies; they just—they just calmly stood there looking on I mean, really, Ron Weasley calmly stood there while Voldemort hovered over his friend? Yeah. There’s no way that’s canon. Ahem. Right. Digressing.)
He doesn’t actually appear in HBP and Ron/Hermione aren’t there to witness any of the memories.
They caught a glimpse of him during the Battle of the Seven Potters, I’ll give you that, we know Ron points out that he can fly so he must have seen him from a distance.
But no, it’s not until the end of Deathly Hallows that Ron and Hermione truly get a look at Voldemort. And it’s when Harry’s ‘dead’. Something about that is shocking but beautifully poetic. Only when Harry falls are they able to face Voldemort and stand their ground against him.