Stupéfier belong to the 1st group. Stupéfier is a common french verb.
Stupéfier is conjugated the same way that verbs that end in : -ier
Stupéfier is conjugated with auxiliary avoir.
Stupéfier verb is
direct transitive. Stupéfier verb is a direct transitive verb, so passive voice can be used.
However, although the terminations are perfectly regular, stem can be irregular and have numerous variations.
Stupéfier is conjugated the same way that verbs that end in : -ier.
STUPÉFIER : v. tr. Engourdir, diminuer ou suspendre le sentiment et le mouvement. Il s'emploie surtout figurément et signifie Causer une grande surprise. Cette nouvelle l'a stupéfié. Ce discours stupéfia toute l'assistance.