格かく段だんの相そう違い

Meanings

1

marked difference; striking contrast

Emphasizes a very clear, significant difference, often used in formal or written contexts.

格かく段だん
An adverb/noun meaning 'remarkably' or 'considerably'; 格段の相違 is a specific noun phrase using 格段 to modify 相違 (difference).
相そう違い
A formal noun meaning 'difference' or 'discrepancy'; 格段の相違 is a fixed compound emphasizing a large degree of difference.

Compound of 格段 (kakudan, 'remarkable') + の (no, possessive particle) + 相違 (sōi, 'difference').