They make blue-black extra hard to fight against because you're never quite sure where the danger lies
Think about the colors the person passing to you is likely to be playing based on all the information you gather, and if you are drafting at your local game store, consider asking them afterwards to check your prediction
Often, the play pattern to punish control decks is to hold a game-swinging card for the post-Wrath turn on curve and put them on the back foot for the rest of the game
To attempt to formalize things a bit further, the new Commander Panel introduced Game Changers, a list of cards whose inclusion marks a more powerful deck
All of them went up in value by a factor of ten or more when Commander broke out
At the end, each player will have about 42 cards, which they can use to build a 40-card deck, adding in any basic lands they need