expression, adverb
above all else; more than anything
Emphasizes that something is the most important or valued among all things. Often used with expressions of feeling, desire, or priority.
何にも増して健康が一番大切だ。
Above all else, health is the most important.
彼は何にも増して家族を愛している。
He loves his family more than anything.
何より is more common and casual, meaning 'more than anything' or 'best of all'. 何にも増して is slightly more emphatic and literary.
From 何 (what) + に (particle) + も (inclusive particle) + 増して (te-form of 増す, to increase), literally 'even more than what', meaning 'more than anything'.