Did Avatar Korra destroy the world?

The short answer needs a distinction

“Did Korra destroy the world?” can mean three things: did she make decisions with lasting consequences, did she physically cause a later catastrophe, or did she intend mass destruction? Those are different questions. The official introductory material does not establish all three just by calling the Avatar a feared figure.

Check the evidence behind the claim

Claim	What the cited introduction supports
The world has suffered a catastrophe	Yes, this is part of Seven Havens' setting
The Avatar is feared and pursued	Yes, this is part of Pavi's situation
Korra intended to destroy civilization	Not established by that premise
The Book 4 finale is itself the later cataclysm	The two should not be treated as identical without further evidence

Why the finale causes confusion

Korra's final confrontation with Kuvira involves spirit energy and the creation of a new portal. The story then continues with survivors and a personal ending for Korra and Asami. A later show taking place in a ruined world does not erase the distinction between those events.

What would settle a stronger claim?

An explicit account of the event, supported by the story rather than only a hostile character's opinion, would be stronger evidence. Until then, it is more accurate to describe Korra's reputation as contested than to present a theory as a solved mystery.

This page assesses the claim against the linked introductory sources. It is not a promise that later episodes cannot reveal new information. Use the cataclysm background for the relevant concepts, and watch released episodes in order before opening detailed theory threads.