性格の強さ /sei ka ku no tsu yo sa/ would mean 'stregth of personality/character. 性格の固さ /sei ka ku no ka ta sa/ also can be used, meaning 'firmness of character'. If you mean something like discipline it is 規律 /ki ri tsu/ meaning 'order, discipline'.
It is "Chikara", meaning power, energy, spirit, or strength. It is a kanji character.
Strength.
The word power, as in strength, is 'chikara,' written: 力
'Chikara' or 'tsuyosa'.
its tuff
grit, guts
Strength...japanese words written as "力(ちから)", pronounced as [ti ka ra]. Improvement: Close enough, yes, but the usual pronunciation is "chikara".
Character development.
In Japanese, "tora" (虎) means "tiger." The character 虎 represents the animal tiger in the Japanese language. Tigers are symbolic in Japanese culture, often representing strength, courage, and protection.
Hello Kitty is a Japanese character because she was produced by the Japanese company Sanrio who continues to market the character to this day.
the character is Chinese (Kanji in japanese), but the pronouciation is Japanese as it had already existed before the character of 犬(inu) entered Japan.
By itself, the reading is kyou, but this is the character that is part of the word kowai, meaning scary.