istima is specifically glossed as "wise (in sense knowing very much)...", so I am hazarding that istare would fit your first word, and indeed nolwe the second.
eldamo.org - Eldamo : Quenya : istima

+Tamas Ferencz That’s a good possibility. The -re verbal noun suffix has often seemed to me uncomfortably similar to the -r agental suffix, especially in plural, but quite a few words use it.

Another possible Q twist would be to use ulundo for the first “monster” and keep úvanimo for the second to emphasize the distinction between “deformed and hideous” and “corrupt or evil”. Of course, this reduces symmetry and may be reading into the those glosses more specifically/literally than intended; but having such subtleties in Q greatly increases its expressive possibilities.

+Robert Reynolds I think by employing two different words for monster you'd lose the word play that makes the quote work in English.

+Tamas Ferencz I agree, and for the same reason. However, in other cases, such options may enable word plays. For instance:

Frankenstein i úvanimo, lá i ulundo.

with deliberately confusing/ironic English rendering “Frankenstein is the monster, not the monster.” (perhaps distinguished in E by vocal inflection)