ボクが憧れたのは翔太部長の『力』じゃない。体を張ってでも信念を貫こうとする雄々しい勇気だったはず。

『』。。

What I looked up to in Captain Shota wasn't his 'strength.' It was, I'm sure, his manly courage to stand by his convictions even if it cost him his body.

Literal

Boku [subject-が] admired [nominalizer-の] [topic-は] Shota captain [gen-の] 'strength' is-not. Body [obj-を] stretching-[even-てでも] conviction [obj-を] pierce-[try-to-しようとする] manly courage was [should-はず].

A cleft construction — '[what I admired was] X, not Y' — built via のは ... じゃない. 体を張る is an idiom meaning 'to put your body on the line, to risk your life'; でも after the て-form makes it 'even if [it comes to that].' 信念を貫く ('to see one's convictions through') is another fixed phrase; the volitional ~しようとする expresses 'trying to X.' 雄々しい is a slightly literary word for 'manly, heroic.' Final はず marks the assertion as the speaker's confident inference rather than direct observation.