So far we know of two versions of the Red Hulk:

The Red Hulk (First appearance: Hulk 1, 2008;) is Thaddeus “Thunderbolt” Ross. This twist reveal was done two years after the first Red Hulk appearance, in issue 23 of the same series.

One is General Thaddeus “Thunderbolt” Ross, yep, the same General who pursued Hulk every single day. After the events of World War Hulk, a mysterious Hulk appeared.

General Ross is a military officer who has been a longtime adversary of the Hulk. To better combat the Hulk and other superhuman threats, Ross undergoes a procedure that transforms him into the Red Hulk. Unlike the green Hulk, the Red Hulk retains his intelligence when transformed and can emit heat and absorb energy.

Over the years, he has been an antagonist and an antihero in various Marvel Comics storylines. The character has appeared in multiple comic book series and crossover events, interacting with other Marvel characters such as the Avengers, the X-Men, and the Fantastic Four.

And he was even capable of providing his daughter Betty with his powers.

But later, Hulk moved around the world when he found a cure to revert the Gamma radiation and removed the Red Hulk powers from both.

Then we have a second Red later. This one is another general, Robert Maverick, who is able to tap into the Red Hulk’s powers by using a Hulk plug-in, but he has limited time to use it. Somehow, his moustache stays on the face after transforming.