Also on the less life situation, you can attack she becomes unblockable, then you can use the extra combat to hit anyone because shes already unblockable for the turn.
I put together Rakdos Karlach + Cultist of the Absolute on day 1 of release and it is the truth. Attacking with a flying 8/7 commander with ward is practically unstoppable. Any cantrip that grants double strike or double power is a 1 hit kill on any player with the extra combat.
Agent of shadow thieves has to be my favorite that you didnt mention. Getting a +1/+1 deathtouch and indestructible on attack is such a great way to snowball her to ridiculous levels. Give her a nazgul battle mase show she is just forcing opponents to sacrifice permanents and blockers
I reqlly like karlach with guild artisan, you can generate tons of treasure to play big threats like dragons, eldrazi etc. I also run sneak attack type effects to get 2 attacks with those threats.
I built the master chef background and have had a lot of success with it. 1/1 counters and a few proliferation triggers and she's swinging for 9 or 10 damage an attack. The theres also alot of mana dorks that can turn into beaters with karlach out. The only problem is it's a little on the spendy side of things
For White, I like Inspiring leader more, just because Swinging with an army of 3/3's out of no where is nice. Especially since most of white's card draw is based off of tokens/small bodies entering. In Blue the only other one I like instead of sword coast sailor is Fae Wild Visitor giving you some blockers to protect against crackbacks... Especially since blue is good at giving just straight unblockability/evasion to creatures. For Black, Agent of the Shadow Thieves is pretty good too giving +1/+1 Counter, deathtouch and indestructible if the first person you swing at has highest life among opponents, can be used with lure effects to turn her into a board wipe or just make it so she survives the board wipe in mp2... Plus extra combats with big beefy demons is always fun In Red I like tavern brawler, because of not only the buff but much needed card advantage. For Green she is pretty crazy with Raised by Giants
Hardy Outlander is lore accurate, and gruul extra combat is well tread. However Fey Traveler has really caught my eye. I think building it like Yuriko and getting evasice creatures in early could net you 6 faerie dragons a turn. Then dragon tempest would be dealing 6, 12, 18 damage alone over 3 turns. Might be too much wishful thinking though I'm pribably going to give it a go.
I think that would be a great idea as a go wide strategy. Karlach is going very aggressive, more creatures mean more damage which is always good. Especially if your opponents don't have any blockers bc their creatures were goaded the previous turn
