How to win with a “weak” Knight?

In Good versus Evil, on Impossible difficulty, I placed Paladins in the first week and headed towards the Warlock. The Warlock had a decent army, including Hydras, and with the traps, he wouldn't let me pass. I don't remember exactly what I did then. But placing Dragons with the Warlock in the second week isn't that easy; you still need 30 gold.

Let's try to keep the discussion about the Knight in this thread. There are many other topics in the section (for example, a general one), where you can discuss other questions.
Alex_R clearly described the strategy for "Good and Evil": in the second week, with 6 Paladins and the rest of your army, you capture the Warlock and then head towards the Dragons. By the way, with good resource chains, you can upgrade Spearmen and/or Swordsmen for free outside the city. Plus, you can buy Medusas along the way. Of course, by the time you storm the city, your hero will already have some levels, specifically in Ballistics and Leadership (otherwise, it will be difficult).