GG5: intenseness; intensity; violence; severity; vehemence; keenness.
～な intense; violent; severe; sharp; fierce; vehement; keen 《competition》.
Other JEs have adjectival/prenominal glosses.

Yes, adjective glosses are better.

激甚	61452	99.6%
劇甚	235	0.4%

激甚災害	40794

激甚	61452
激甚さ	93
激甚が	53
激甚は	44
激甚を	278	
激甚の	1229
激甚な	4871

https://kotobank.jp/jeword/激甚
彼は激甚な競争を勝ち抜いてきた
He came through successfully in very tough competition.

sankoku does not list this as [n] at all, and specifically gives 激甚さ as a noun form.  One way or the other, primarily as an adjective, so glosses should be adjectives I would think.

I'm not sure I see the kokugo support for "keen". Maybe in something like "intensely interested" could get you there, but that seems very particular...

@@ -11,0 +12 @@
+<ke_inf>&rK;</ke_inf>
@@ -22,5 +23,5 @@
-<gloss>intenseness</gloss>
-<gloss>violence</gloss>
-<gloss>severity</gloss>
-<gloss>vehemence</gloss>
-<gloss>keenness</gloss>
+<misc>&form;</misc>
+<gloss>intense</gloss>
+<gloss>violent</gloss>
+<gloss>severe</gloss>
+<gloss>vehement</gloss>