His pictures can be misleading. They tend to project him as a cold, stiff-nosed and arrogant CEO.
Mr Mittal says organised retail will change the face of India
In real life, he's friendly and warm. He's one of those rare head honchos who'll personally return calls.
But more importantly, he's probably the most-successful Indian businessman in the post-reforms era, after the country embarked on the liberalisation path in 1991.
Meet Sunil Mittal, who controls the $2.5bn Bharti group in India with interests in telecom and retail, and has struck a joint venture deal with Wal-Mart, the US retail giant.
After leading the decade-long revolution in mobile telephony, and bagging the largest customer base of 27m, he's today enchanted with retail and agriculture.
"We're in the final lap of telecom. Now, new areas fascinate me. I am passionate about both retail and agriculture. It's the next big opportunity," he told a newspaper in April this year.
Unlike the huge European-style outlets, India needs the Thailand-type of stores that are "small, air-conditioned, comfortable and don't scare people away".
He's reiterated several times that a such a model would work in India.
The retail foray by Sunil Mittal - no relation to Indian steel magnate Lakshmi Mittal - is an indication that he can quickly spot opportunities in the sunrise sectors.
In the 1970s, he set up a cycle parts business in the Indian state of Punjab.
He came to Delhi in 1981, when he realised he could make a killing by importing portable generators from Japan, where the profit margins were as high as 100%.
During the 1980s, he lobbied the government to allow private firms to manufacture landline sets, and was the first to enter this booming business.
When India opened up the wireless telephony segment in the mid-1990s, he was among the first movers.
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"Then, it was difficult to convince customers to buy a mobile handset for 40,000 rupees($890), pay 16 rupees (35 cents) a minute for outgoing calls and also pay for incoming calls," he told a news magazine.
Worse, policy changes and legal battles restricted the growth of the Indian mobile business in those early days.
But Mr Mittal knew it was only a matter of time before the mobile revolution took off.
Aided by recent policy changes, he slashed tariffs to a maximum of 1.20 rupees (two cents) a minute. What helped was that the price of a mobile set crashed to as low as 2,000 rupees ($44).
Today, Bharti (Airtel), his mobile telephony company, is adding a million customers every month.
Mr Mittal thinks retail is the next growth sector.
The potential can be gauged by the fact that India's retail market is pegged at over $200bn, and organised retail constitutes over $6bn.
Several Indian businessmen like Mukesh Ambani of Reliance Industries, India's largest private sector company, are pumping in huge sums to fulfil their retail dreams.
For Bharti too, access to finance won't be a problem because Mr Mittal is known to be a finance whiz kid, an excellent negotiator and adept at raising cash.
In the past, he has sold stakes in Bharti's telecom ventures to several strategic investors at seemingly attractive prices. He has also innovatively financed his expansions.
Another advantage is that Mr Mittal has the ability to manage foreign partners.
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He surprised most critics when he got SingTel to invest in his telecom venture.
He shocked them when he got a global competitor, Vodafone, to buy a minority stake.
"We have an Asian powerhouse and a global behemoth, this gives us the benefit of both worlds. We're creating value for them, I don't see either of them exiting," he said in a recent interview.
After bagging two of the most successful mobile firms, Bharti plans to spread its tentacles overseas, and buy out small and medium-sized firms in other emerging markets.
It also hopes to grab licences for mobile services internationally.
In the near future, however, telecom will take up only a quarter of Mr Mittal's time.
His focus will be on retail and agriculture, where he wants to be the pioneer to sow the seeds for India's second green revolution.
This is what he said of the future possibilities in a recent interview: "Many summers ago, it was telecom and, fortunately, I was there. Now the train is back at the station and I once again have an opportunity to hop onto it. Organised retail will change the face of this country."