MTL - Invincible Exchange System - Chapter 71 Be reckoned with

Mark is a genius military weapon designer who was kidnapped by a mafia gang after refusing to work for them.
They forced him to design unique weapons for five years, until one day he successfully escaped only to get shot by his trusted comrades.
*Ding! You awakened a weapon system.
When he opened his eyes, he was in a different body and in a different world.
"You want to kill a wild boar without being detected? Forget about bow and arrow. Here, I present you this sniper rifle."
"You want to kill a horde of goblins from the sky? Forget about those flying carpets and brooms. Here, I present you the fighter jet."
"You want to kill a dragon? Forget about taking the help of the S-class adventure team. Here, I present you a nuclear bomb."
Join Mark Spencer/ Lu Zhen as he brings the whole world to its knees with the help of his weapon system.
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Note: Author isn't born in an English-speaking nation and has no editor either. So, please be understanding if there are any grammatical errors.
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My GPA is lower than a slime’s mana.My name is Atheron il Ataraxia, and I’m the walking disgrace of the Royal Academy of Magic.I’ve been held back twice, my essays are used in class as examples of how not to cast spells, and professors sigh in relief when I don’t blow something up during morning lectures.Truth is? I don’t even like this world.I was summoned. A girl from this world pulled me in like a card from a cursed deck, and now I’m stuck living here. Attending classes, battling evil spirits, and dealing with stuck-up nobles whose names are longer than my backstory.But something’s off. My mana doesn’t behave like theirs. The world listens when I speak. And the whispers I hear at night? They’re getting louder.They say evil spirits wander through Ashgrad under the light of the moon. And I think they’re looking for me.They think I’m a failure.Maybe I am.But if this cursed academy wants to survive the next full moon, they might just have to rely on me — the last-ranked summon with a dangerous secret.

Eight hundred years ago, Xie Lian was the Crown Prince of the Xian Le kingdom. He was beloved by his citizens and was considered the darling of the world. He ascended to the Heavens at a young age; however, due to unfortunate circumstances, was quickly banished back to the mortal realm. Years later, he ascends again–only to be banished again a few minutes after his ascension.

Now, eight hundred years later, Xie Lian ascends to the Heavens for the third time as the laughing stock among all three realms. On his first task as a god thrice ascended, he meets a mysterious demon who rules the ghosts and terrifies the Heavens, yet, unbeknownst to Xie Lian, this demon king has been paying attention to him for a very, very long time.

- Description from Novelupdates

After the Fall of Guardian God. His legacy was passed on to Zack. Zack, Who was quite ambitious and Powerful. Can He follow the footprints left behind by the Guardian God or Forge own damn legacy till the end?

He is Smart, Calm, and Collected. Decisive during decision-making. He learns and grows. In the world of Humans, Monsters, and other unknown species. How is he going to overcome the challenges? and began his journey towards the Unknown.