威勢 いせい
isei

Noun

1. power; might; authority; influence

かれ、今 いまのところは とり とす いきおいだけれど、あの威勢 いせいいつまでもつのか、疑問 ぎもんだね。
kare imano tokorowa tobu torimo otosu ikioidakeredo ano isēitsumade motsu noka gimondane.
He's unstoppable right now but the question is how long he can remain at the pinnacle of his career.
Noun

2. spirits; vigor; vigour; energy; boldness