“sila” is strength, not power. Power is “vlast.”
"He is forceful" if you insist on playing this game. Another derived adjective if forcible but it has a bit more elusive meaning (forcible entry into a building)
Thanks for the laugh. An automated translation tools, especially dumbed down online ones, never work right because they don't have a context or a means to provide it.
https://en.wiktionary.org/wiki/%D1%81%D0%B8%D0%BB%D0%B0#Russ...
https://en.wiktionary.org/wiki/%D0%B2%D0%BB%D0%B0%D1%81%D1%8...