Magic is a very complicated subject. It actually involves math, physics, chemistry, even biology to some extent.
Firstly, a magic spell is dependent on three aspects of a person: mental power, affinity, and mana pool.
To use a certain type of magic, the user must have the affinity in that particular element, or else they would take an extremely long time to master. On the other hand, if the affinity is high, the magic-user will take less time learning, the mana consumption also decreases, and it is more powerful in general. This is exactly the reason why people would just focus on their given attributes. Learning other elements would be too wasteful.
The highest grade of affinity is total affinity, which has absolute domination over fire, water, wind, earth, light, and void. These are basically natural talents. There are items that can increase affinity, but talking about them for someone like Hero is pointless, and Sam cannot have access to them anyway. Prices of said items can actually be astronomical to the point of being a political or economical weapon. For someone with a background like Sam, there was no way for him to get his hands on those.
Secondly, a mana pool is a must to practice magic. Its importance is similar to the battery of an electric car. Without a good mana pool, one would lose their ability to conjure up spells in combat. Luckily, the mana pool is like muscles in the body. Mana particles in the environment will be stored inside the cells in the body just like how protein and lipids are stored. Through constant practice, the mana pool slowly gets bigger. However, the rate of which is dependent on the magic-user. The mean expansion according to research is 25% per year.
Hero's mana pool expansion rate is 4 times that amount. As if that was not enough, he was born with a mana pool that has double the size of a normal person. In short, each year, Hero has his mana capacity double every year. By the time he was 18, his mana pool compared to the average was already 10 times larger. This allows the Hero to use spells at a ridiculous amount without feeling burned out at all.
Sam's mana pool although not very good, was very close to average. So the difference between the mana pool of the two is about 10 times.
Next would be an unquantifiable aspect of magic spells, the mental power. To conjure up a magic spell, the user must first think of what they would need. Visualizing the spell is the only way to accurately perform magic. The more vivid, the better. Once the magic has been formed, concentration is needed to keep the mana from dispersion. In short, mental power is required to start and maintain a magic spell. Although until today, researchers still have not found an accurate way to measure mental power, it is indeed a really important aspect of a spell. At the moment, mental capacity is similar to an invisible resource inside of one's mind.
Thankfully, Sam's mental energy has always been pretty strong. At least he can fight the Hero on more or less similar ground if they are only fighting with their minds like that.
But still, what are the odds of the Hero losing?
Affinity, check.
Mana pool, check.
Mental power, similar.
Just by looking at the differences, anyone can easily tell that Sam is going to lose. Drastically.
So who gave him the idea to challenge the Hero? Is he out of his mind?
As a matter of fact, Sam is out of his mind.
His head is filled with envy, his eyes have lost their focus. The basic reasonings are gone due to him being unable to control his emotions. The forces of the world have made sure that he would become a good stepping stone for the Hero. When Sam was talking to him, the other party could see nothing in his eyes but a swirling vortex of dread, which he found very similar to how Marie was looking at him whenever he happened to talk with another girl.
Furthermore, facing a challenge from someone clearly weaker than him, Hero has no way to decline the offer. He is the embodiment of Hope for the country, the biggest prodigy. If the Hero were to reject Sam, people would immediately look down on him. They would not make a big idea out of it at first. However, after a while news would travel everywhere that the Hero is spineless, not being able to take on a simple challenge from someone immensely weaker.
"What do you have to offer?" Looking at Sam, the Hero says.
"My life." A coarse voice from Sam.
"H..hey. Don't joke around like that!" Hero is taken back by that reply.
"I'm not kidding. Marie is gone. My life has no meaning anymore. All of my time up to this point has been used for a future together with her. She is with you now. So I guess I should leave as well."
At this point, the classroom has gone incredibly silent to listen in. The conversation is really interesting.
It's a love quarrel.
A common theme. Nothing too weird. They have seen that a lot. Though Sam challenging someone leagues above himself is still fascinating to look at.
"So you're saying that you would like to die under my hands?" Hero looked at Sam carefully.
"Either that, or you'll die under mine."
No one laughs or even says anything. The topic although is really heavy, yet everyone is just enjoying themselves rather than stopping it. It seems that to them something like this is not unexpected. To someone like Hero, who was originally from a peaceful world, he is not getting it one bit. He just could not understand why Sam would challenge him to a death match while knowing the difference between the two.
Unbeknownst to Hero, love is a powerful drive on this Earth. Anything abnormal if put on a 'love' tag, would become normal.
In fact, the Goddess of Love is just a short name.
Her full name is the Goddess of Love, Envy, and Jealousy.