In the realm of 'Attack on Titan', Eren Yeager, possessing the Founding Titan, is essentially the strongest. However, the true power of the Founding Titan can only be realized by someone of royal blood. Despite its perceived pacifist nature, it harbors the capability to control all titans and alter the memory and biology of Eldian people. Mindblowingly powerful, isn't it?
On the other hand, the Attack Titan's strength lies in its tenacity, symbolizing the relentless pursuit of freedom. It's like comparing a master tactician and a furious warrior. Personally, I admire the Colossal Titan, a literal embodiment of raw power and destruction.