Play the combat with Beastmen. It is so fun. I love watching my minotaur charge into infantry. They go sailing through the air in a cloud of blood.
I just finished a 21 hour campaign on Stellaris. I was the Imperium of Man, a Militaristic Authoritarian Materialist Human Imperium. I ended up going full synthetic and became the Adeptus Mechanus. Very powerful conversion.
The best part was that I ended up spending almost 200 years gearing up to face off toe to toe with the Awakened Empire, the Directors. They were by far the most powerful empire and right on my border. I cultivated the right tech to face them, flak cannons, kinetic batteries, and Mega cannons. I got the perk that gives +33% damage against awakened and stagnant empires. I built a fleet with a capacity of 2200. I managed to catch on of their 260k fleets alone and killed it. And then we had two 600k fleets collide in a sector we both controlled a planet in. I annihilated them, losing about 150K but completely destroying them. I then captured two of their ring worlds and 5 planets that were already within my Empire's borders, and accepted peace.
The game was finished at that point. I made a quick war to vassalize the second largest remaining empires which allowed me to hit 40% and win.
Great game and satisfying to have my centuries long plan come to a successful conculsion!