Invincible in Douluo After Getting German KARDS

[Douluo + KARDS Germany + wilderness survival + no female lead + multi-protagonist world conflict + realism + spy organization]

After transmigrating to Douluo Dalu, Luo Ning unexpectedly gains a Kards national-card Martial Soul. At his first ring, he obtains Germany, the supreme nation card, and begins his path to invincibility.

As his level rises, Britain, the Soviet Union, Japan, the United States, and others all become stepping stones on his road to strength.

But clearly, this world has far more enemies than he ever imagined...