にすぎない・でしかない・にほかならない: the difference
にすぎないN2
Meaning
No more than, Just, Merely
Past papers
Tested 3 times in past papers
Example
君は学生にすぎない。
You are nothing more than a student.
でしかないN2
Meaning
Merely, Nothing but, No more than
Past papers
Tested 3 times in past papers
Example
あの人は見栄の塊でしかない。
That person is nothing but the embodiment of vanity.
にほかならないN2
Meaning
Nothing but, None other than, Simply
Past papers
Tested 2 times in past papers
Example
第一にすべきは人命にほかなりません。
The first priority is nothing other than human life.
How to tell them apart
「にすぎない」: low degree, nothing beyond; stresses limited amount or value: 「彼はまだ子供にすぎない」 (He is still just a child).
「でしかない」: declares 'it is this and nothing else'; more subjective and sharper.
「にほかならない」: the opposite, the strongest affirmation: 'it is none other than...'.