Aquaman suffers a devastating personal tragedy as an old enemy targets him for revenge.
And then there was the impact on Aquaman in-universe - his son's death devastated him. (Naturally.) It eventually ended up breaking up his marriage to Mera and put him through a hell of an emotional wringer that he was still dealing with decades later. It also elevated Black Manta from recurring nemesis to arch-enemy status, and every time they fought after this story, Aquaman was out for Manta's blood. (At least until Aquaman's history was completely wiped clean by the post-Flashpoint New 52 continuity - in current continuity, Aquababy was never born, let alone killed.)