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They're saying the iPhone is the grim reaper of the internet.
Literal
iPhone [topic-は] internet [with respect to-にとって] death-god [explanatory-なん][quotative-だって].
A casual, internet-commentary kind of line. ~にとって ('for X,' 'from X's perspective,' 'with respect to X') marks the party whose interests or point of view matter — here, the internet is the one being impacted. 死神 (しにがみ, 'death god,' 'grim reaper') is a Japanese counterpart of the Western reaper, but also a common figurative term for something that brings doom or harm. The ending なんだって is the casual spoken form combining なん (explanatory なのだ) + だって ('[I heard] that X,' 'they say X') — a hearsay marker for reporting something someone else said or a rumor in circulation. The speaker is passing on a claim, not committing to it.