You can give your opponents planeswalkers more loyalty, increase the number of +1/+1 counters on their creatures, or even just give them additional resource counters like oil counters
Kaalia is has been among MTGs best commander decks for a long time because cheating mana costs is almost always broken, so with Kaalia you want the biggest, baddest creatures of the types you can find, like Avacyn, Angel of Hope or Vilis, Broker of Blood
Caesar hits so many favorites for me: hes inexpensive, hes got a decent power and toughness, and with a little sacrifice, he becomes a problem quickly while doing everything that Soldiers wants to do, make more Soldiers and deal damage
Brawl Not Legal Vintage Legal Timeless Not Legal Commander Legal Pauper Legal Oathbreaker Legal Penny Not Legal Toolbox Buy This Card Notes and Rules Information for Drain Life: Cost reducers can be used to reduce the X part of the mana cost
Black I think the highlights in black come as cards that look and feel as if they were always in the old border, even though we know that to be untrue