This is the 9141st most frequent Japanese word.
焦がさ
"焦がさ" is not a standalone word but resembles a conjugation of 焦がす (kogasu), meaning "to burn" or "to scorch."
Here, '焦がさせて' means 'to burn away emotionally or metaphorically,' referring to the negative impact his lack of effort had on his future.
彼は努力しないことが自分の未来を焦がさせてしまった。
His lack of effort burned away his future.
In this sentence, '焦がさない' means 'not to burn,' used literally regarding the cooking process.
料理を焦がさないように、弱火で加熱してください。
Cook on low heat to avoid burning your food.
Here, '焦がして' is used metaphorically to express a strong emotional impact, symbolically setting the heart 'ablaze' with feelings.