Ci talk:1015682538
This entry contains a note "vfe2b3" and I have checked that 一此为甚 is indeed in Far East, but I think 一此为甚 is wrong. (Specifically, I think the second character should be 之.) The headword (and definition) was copied from the Far East dictionary, but I think Far East was probably wrong. 一此为甚 appears on only one page on the entire Web according to Google, and it is not used in context on that page; it is simply listed as a (supposedly) Chinese phrase. Here is the page: [1]
There is another entry ABC copied from Far East: 一之为甚 One mistake is enough. That one is correct, and Google says there are about 300,000 webpages containing that phrase.
ABC also has an entry for 一之谓甚, which is on about a quarter of a million webpages according to Google.
I suggest considering 一此为甚 for deletion.