The Sloan Great Wall held the record for a decade: a complex of galaxy superclusters spanning roughly 1.37 billion light-years identified in the Sloan Digital Sky Survey, nearly three times the length of the CfA2 Great Wall that first revealed the universe's sheetlike organization (Gott et al. 2005; Park et al. 2012). It is not a gravitationally bound object, but its parts form a coherent, connected configuration that any structure-formation theory must be able to produce.
ΛCDM strains to produce it. Hierarchical clustering grows structure from the bottom up at rates fixed by the matter content and the initial fluctuation spectrum, and those rates cap coherent assembly at a few hundred megaparsecs within the age of the universe. The Sloan Great Wall sits beyond the comfortable range, and it crowds the homogeneity scale, the distance beyond which the cosmological principle says the universe should average out featureless. The standard defenses are statistical: in a big enough volume, percolation links unrelated overdensities into apparent giants. The defense weakens as the giant-structure census grows, because each new wall, ring, and arc requires its own independent stroke of pattern luck.
The standing is a population argument now rather than a single-object dispute. The Sloan Great Wall anchors the middle of the giant-structure size spectrum, between the CfA2 Wall below and the Hercules-Corona Borealis Wall above, and DESI and Euclid will map that spectrum across volumes where the statistical defenses become quantitatively testable.