Tactics against the Tower.

Yes, we got sidetracked... Let's get back to the question. Try playing as Necromancers, gather skeletons from neutral creatures, and build and upgrade vampires. Necropolis is the cheapest castle, and upgraded dragons will effectively deal with enemies. Or, marsh-upgraded gorgons can easily eliminate titans with +2, +4 (depending on the situation). Or, if you have archangels left, you can resurrect someone. There are many options. And I can't guarantee that your friend won't come up with something brilliant. Maybe he's just playing better than you?