rightwise
Rightly (correctly or justly); rightfully.
rare
And, after that fourth trial, sundry of the kings and many of the lesser barons and knights and all of the commons cried out that these were trials enough, and that Arthur had assuredly approved himself to be rightwise King […]
Where it comes from
Presumably from Old English rihtwīs, reinforced by reanalysis as right + wise.
Adapted from the Wiktionary entry rightwise (CC BY-SA 4.0).