The Cree word mituni is frequently used, especially with Cree verbs (that have a meaning like European adjectives).
The word vre (French vrai 'real') is used as well, but more frequently with nouns than with adjectives (aen vre smart 'a really smart person').
Reduplicated French adjectives are also used for strengthening an adjective.
Source: Laverdure & Allard 1983: 47-48
Source: Laverdure & Allard 1983: 226
Source: Laverdure & Allard 1983: 160
Source: Fleury 2007