Synonyms for Truly (same or very similar meaning)
WordNet sense 1 (with sincerity; without pretense):
sincerely, unfeignedlyWordNet sense 2 (by right):
rightfullyWordNet sense 3 (in fact (used as intensifiers or sentence modifiers)):
really, in truthWordNet sense 4 (in accordance with truth or fact or reality):
genuinelyFrom the ODE community, based on WordNetadd/edit