I love how when it comes to Bellatrix, Rowling reaches for the most extreme language available to her in the entire series for Voldemort, and only ever about her. His emotional ceiling, in both directions, is her. Bellatrix Lestrange. The highest high and the most devastating low, and they both point to one woman.
And look at what doesn't reach those extremes. His rebirth in the graveyard, arguably the most significant event in his life since his fall, doesn't register through the scar connection as the source of such immense joy. On the other end, losing his Horcruxes, pieces of his soul, produces rage, yes, but it's never described with anything approaching the force of a bomb. Nagini's death, which makes him mortal again for the first time since he was teenager, does not affect him with anything approaching that intensity. Those are all significant moments and not one of of them affects him like Bellatrix does.
The emotional spectrum of the most self-interested character in the series has Bellatrix at both poles. Bella is both the thing that makes him happiest and the thing whose loss devastates him most. Not his body, not his immortality, not his political power, not his prophesied enemy who caused him to lose his body for fourteen years. Only Bellatrix and nothing and nobody else.
Rowling gave him those superlatives twice, only twice, and pointed them both at the same woman.
This is just what what the text explicitly says 🖤