に至(いた)ってはWhen it comes to, As for, In particular, What is worse or more

Both relate to reaching a point, but the function is different. に至って・に至り marks the point at which a result, realization, or change finally occurs after preceding circumstances, often corresponding to ‘not until’ or ‘only when,’ as in 先輩に注意されるに至って、自分の間違いに気づいた (‘I didn’t realize my mistake until I was warned by a senior.’). に至っては is used to single out an extreme or noteworthy example within a broader situation, adding emphasis similar to ‘what’s more’ or ‘even,’ as in 母に至ってはインターネットさえ使えない (‘What’s more, my mother can’t even use the internet.’).

Both refer to an extreme point or example, but with opposite nuance. に至っても means ‘even after reaching (that point),’ emphasizing that a situation or attitude does not change despite time, experience, or progress, as in 注意されるに至っても態度は変わらなかった ('Even after being warned, his attitude did not change.'). に至っては singles out a specific case or stage as especially noteworthy or extreme within a broader situation, often with emphasis like ‘when it comes to’ or ‘even,’ as in 母に至ってはインターネットさえ使えない ('When it comes to my mother, she can’t even use the internet.').

Both expressions can convey the idea of 'particularly', but in different ways. に至っては presents an extreme example of something previously introduced. For example, when talking about a region with a lot of snowfall, A市に至っては60センチも積もることがある ('In particular, city A sometimes has accumulation of 60 cm.'). In contrast, に限って is often used when some unexpected/undesired action happens 'particularly' or 'only' at certain times, e.g. 忙しい時に限って誘ってくる ('He invites me particularly/only when I'm busy.').