What is andrew carnegie most well known for? mechanizing every stage of textile production creating the largest, most powerful companies the world had seen founding one of the world’s first modern research laboratories patenting more than one thousand inventions

The answer is creating the largest, most powerful companies the world had seen
His company regarded as the most powerful because at the peak of his power, he managed to monopolized the entire Steel industry by buying all of his competitor, every single one of them.
If the value of Carnegie's wealth is formulated in the year of 2017, he has a net worth of around $300 Billion (five times richer than bill gates)

He is most well know for B. creating the largest, most powerful companies the world had seen