What makes an athlete tough? Is it succeeding on the field, court, or course despite overwhelming odds? Is it competing through pain? Is it staying the course when it's so easy to call it quits? Is it prevailing in the face of perceived limitations? Is it leading your teammates and your community?

Yes, yes, yes, yes, and yes. Toughness is a combination of all of the above. It's impossible to pick the toughest athletes of all time, but we're committed to trying. The seven legendary athletes below are tough by every measure. They're gamers, fierce competitors, leaders, activists, survivors, and trailblazers. 

Who did we forget? Who else should be part of this exclusive club of insanely tough athletes? Let us know on Instagram.

7 of the Toughest, Most Badass Athletes of All-Time

1. Jackie Robinson

When Jackie Robinson was called up by the Brooklyn Dodgers in 1947, becoming the first African American to play in a Major League Baseball game, he was subjected to horrible racism, even in his own clubhouse. Some of his own teammates threatened not to play alongside him, and opposing players and teams threatened not to take the field against him. Those turned out to be empty threats, but the punishment on the field was real. Robinson was called derogatory names by hate-filled players and fans, and was the victim of some extremely dirty play on the basepaths.

Despite all of the persistent hate, Robinson was able to drown out the noise, become a champion for civil rights, and blossom into a superb player. Amidst unthinkably poor circumstances, Robinson excelled on the field, winning an MVP and a batting title and making six All-Star teams. He played through absolute hell, and came out the other side a Hall of Famer and cultural icon.

Related: 10 Iconic Athletes That Broke Barriers and Changed the World

2. Simone Biles

Simone Biles has been overcoming obstacles ever since she was a little girl, when she was in and out of foster homes. En route to becoming perhaps the greatest and most celebrated gymnast of all-time, she claims that she was sexually abused by former USA Gymnastics team doctor Larry Nassar. 

“I am much more than this,” the four-time Olympic gold medalist wrote on Instagram. “I am unique, smart, talented, motivated, and passionate. I have promised myself that my story will be much greater than this, and I promise all of you that I will never give up. I will compete with all of my heart and soul every time I step into the gym. I love this sport too much and I have never been a quitter.”

Related: Simone Biles Crushed Her Boyfriend — an NFL Safety — in the Rope Climb

3. Brett Favre

Hall of Fame quarterback Brett Favre is remembered most for his cannon of an arm and a burning competitive fire and will to win. Just as impressive, if not more so, was his incredible durability and willingness to play through pain. Despite playing a punishing position, in which he was often left vulnerable to huge hits and takedowns every single time he took a snap, the iconic QB rarely came out of a game. How much of an ironman was he? Between 1992 and 2010, Favre started 321 consecutive games (including 24 in the playoffs), the most in NFL history. With all due respect to Cal Ripken Jr., baseball's ironman who played in 2,632 consecutive games, Favre's record is more impressive.

4. Serena Williams

Tennis icon Serena Williams has been vocal about the racism, sexism, and body shaming that she's encountered, beginning when she was an up-and-coming teenage prodigy and continuing into her legendary career as a 23-time Grand Slam singles champion. And at the risk of alienating large swaths of her fanbase, she's been extremely vocal in standing up for herself, fellow women, and the African American community. The 39-year-old never let the detractors distract her. On the contrary, she cemented herself as perhaps the greatest tennis player to ever step on a court.

Need more proof of her toughness? In 2017, she won the Australian Open while she was two months pregnant. Later that year, less than fourth months after giving birth, she returned to the tour to compete.

Serena also gets bonus points for the fact that she's crushed two Spartan races. 

5. Jim Abbott

Born without a right hand, Jim Abbott defied all of the odds to make it to the major leagues. Despite the fact that he clearly had a remarkably strong left arm, scouts were wary of signing him due to his disability. He proved himself over and over again, even as opposing offenses tried to take advantage of his perceived limitation by bunting, forcing him to field with only one hand. Unbelievably, Abbott devised a system in which he would slip his hand into his glove the moment after he released the ball, in time to field a potential comebacker. He did this after every single pitch of his career.

The highlight of Abbott's inconceivable career came in 1993, when he tossed a no-hitter for the Yankees. Six years later, he made more history when, batting with one hand, he ripped two hits for the Brewers.

Related: These Are the 5 Toughest Movie Characters of All Time (and Why)

6. Logan Aldridge

When Logan Aldridge was 13 years old, the former competitive wakeboarder's left arm became entangled in the propellor of a boat, cutting through his muscles. After numerous failed attempts to save it, Aldridge's arm was amputated above the elbow. After the initial shock and devastation, he had an epiphany — courtesy of his loving mom — that would change his life: "It's just an arm."

Aldridge continued to pour himself into athletics and fitness, eventually earning a reputation as the fittest one-armed man in the world. Among his most notable accomplishments, Aldridge set two Guinness World Records: the most one-arm, one-leg push-ups in 1 minute (26) and the most weight lifted by single-arm barbell cleans in 1 minute (2,025.01 pounds). Check out his appearance on Don't Break With C.T. Fletcher below, where he crushed a 209-rep deadlift marathon.

7. Rea Kolbl

Rea Kolbl is toughness personified. Born and raised in Slovenia, she was a competitive gymnast before moving to the United States at age 19, where she earned bachelor’s degrees in physics and astrophysics from UC Berkeley and a master’s degree in science and engineering from Stanford. When she wasn't hitting the books, she was running, training, and quickly establishing herself as a world-class endurance athlete and obstacle course racer. Unflappable and indefatigable, Kolbl has won World's Toughest Mudder twice — completing a record 90 miles in the 24-hour race the first time — and she also took first at the Spartan Ultra World Championship, also a 24-hour race, in -22°C amid continuous snowfall. Adding to her legend is the fact that she has topped some of the best male racers in the world on numerous occasions.

Read more about her inspiring story here, and click here to train like her for a week.