mightly
Mighty; competent; capable; strong; powerful.
King Haco would have ſtay'd, notwithstanding the mightly Power he had to encounter, […]
Substantial; weighty; of import.
In touching upon these mightly results, which must attend, or soon follow, the completion of Welland Canal, [...]
Able; able to occur; possible.
Where it comes from
From Middle English mightli, myȝtly, from Old English mihtelīċ (“possible, able, capable”), from Proto-West Germanic *mahtilīk, from Proto-Germanic *mahtilīkaz, *mahtulīkaz, equivalent to might + -ly. Cognate with Swedish maktlig (“powerful”).
Adapted from the Wiktionary entry mightly (CC BY-SA 4.0).