Make Strong in Chinese / Japanese...

精神力量 is a title that speaks of one's soul or spirit and the capacity or strength that soul possesses.

The first two characters mean mind, heart, spirit, and/or soul.

The last two characters mean strength, capacity, or ability.

Note: Separately, these are two words in Japanese and can be pronounced, but this does not make a natural title in Japanese (best if your audience is Chinese).

不屈不撓 means “Indomitable” or “Unyielding.”

不屈不撓 is a long word by Chinese standards. At least, it is often translated as a single word into English. It's actually a proverb in Chinese.

If you want to break it down, you can see that the first and third characters are the same. Both mean “not” (they work as a suffix to make a negative or opposite meaning to whatever character follows).

The second character means “bendable.”

The last means “scratched” or “bothered.”

So this really means “Won't be bent, can't be bothered.” I have also seen it written as “Will not crouch, will not submit.” This comes from the fact that the second character can mean “to crouch” and the last can mean “to submit” (as in “to give in” such as “submitting to the rule of someone else”). This may explain better why these four characters mean “indomitable.”

Notes:
Some will translate this as “indomitable spirit”; however, technically, there is no character to suggest the idea of “spirit” in this word.
Other translations include indefatigability, indomitableness, or unremitting tenacity.

The first two characters can be stand-alone words in Chinese.
In Japanese, this is considered two words (with very similar meanings). It's more common to see the word order flipped to 不撓不屈 in Japanese.
The same characters are used in old Korean Hanja. Just like in Japanese, the words are swapped to 不撓不屈 creating a word pronounced “불요불굴” in Korean.

See 不撓不屈

See Also:  Tenacity | Fortitude | Strength | Undaunted

自由意志 is a concept that has existed for thousands of years that humans can understand right and wrong, then make a decision one way or the other (thus affecting their fate).

Sources such as Confucius, Buddhist scriptures, the Qur'an, and the Bible all address this idea.

As for the characters shown here, the first two mean free, freedom, or liberty. The last two mean “will.”

Can be romanized from Japanese as jiyū-ishi, jiyuu-ishi, and sometimes jiyuu-ishii.
It's 자유의지 or jayuu-yiji in Korean and zìyóu yìzhì in Chinese.

See Also:  Freedom | Strong Willed | Fate

This can be translated as unwavering determination, unwavering resolve, or strong determination.

堅定 means unwavering, firm, steady, staunch, and/or resolute.

決心 means determination, resolve, resolution, determined, firm and resolute, or to make up one's mind.

If you want a longer version, 堅定不移的決心 is also a popular phrase with a similar meaning. Contact me if you want that instead.