1 Soon as the cruel flames slaked were,
Soon > [As soon]
2 Malbecco, seeing how his loss did lie, 3 Out of the flames, which he had quenched whilere,
whilere > erewhile: a while before
4 Into huge waves of grief and jealousy 5 Full deep implunged was, and drowned nigh,
Full > Very implunged > plunged into (the prefix is here tautological, and thus intensive)
6 'Twixt inward dole and felonous despite;
dole > grief, sorrow felonous > {Cruel, wicked, befitting a felon} despite > malice; rage
7 He raved, he wept, he stamped, he loud did cry, 8 And all the passions that in man may light
light > be incident; hence: occur