Marchesa, the Black Rose EDH (test configuration) (EDH / Commander)

(not up to date)

The general Combo:
A creature with ETB/die-Effect + sac outlet + counter distributor

Counter distributors are:
Creatures with graft*, Mikaeus, the Unhallowed, Metallic Mimic, Unspeakable Symbol, Feast on the Fallen (and Spark Double in an idirect way)

*reset them by sacrificing them before the last counter is used (don't be fouled by their second ability, graft is what matters!)
The graft-creatures are: Cytoplast Manipulator, Vigean Graftmage, Helium Squirter and Novijen Sages

Of course you can also generate counters by attacking, but this way you only get one ETB/die-trigger per round, so you generally want to assemble a combo.
To reliable use dethrone you can lower your life total by using your lands (or Unspeakable Symbol (and even Goblin Bombardment or Flayer of the Hatebound if times are dire)).

Some creatures generate their own counters and work without a special counter distributor or dethrone.
These are: Thought Sponge (most of the times just a better Consecrated Sphinx), Flayer of the Hatebound, Patron of the Vein (great with Butcher of Malakir) and the graft creatures (They don't have ETB-effects of their own but work great with Grave Pact, Butcher of Malakir, Grim Haruspex, Yawgmoth, Thran Physician, River Kelpie, Flayer of the Hatebound or even Ashnod's Altar.)

Other Combos:

Feast on the Fallen + Goblin Bombardment / Flayer of the Hatebound
also great with Kokusho, the Evening Star / Gray Merchant of Asphodel / Tuktuk Scrapper

Cytoplast Manipulator + Forge of Heroes / Unspeakable Symbol / Graft creatures in general
Tip: If Cytoplast Manipulator would leave the battlefield (or you want to sac it to reset its counters), you can sac the creatures you have taken control of with it before. Because they allready have a counter on them, they will return to you at the beginning of the next end step and won't go back to their owner.

Blade of Selves + Tuktuk Scrapper (all Allys see each other) / Kokusho, the Evening Star / Keiga, the Tide Star and generally every creature with an ETB-effect (especially Patron of the Vein for not only removal but a lot of damage in the air)
Also Blade of Selves + Gray Merchant of Asphodel is a nice Combo since you get 3 ETB-triggers and 6 additional devotion (draining your oppenents for at least 16)
and of course Blade of Selves + Massacre Wurm to give all your opponents creatures -6/-6 and make them lose 8 life for each dying creature.
Blade of Selves is basicly a two card combo with any ETB-Creature

Unspeakable Symbol + Crystalline Crawler (life for mana)

Razaketh, the Foulblooded + Ever After (sac a creature to search for Ever After, play Ever After to reanimate to creatures (Ever After goes under your deck), repeat)

Jokulhaups + Marchesa (destroy all creatures, artifacts and lands, but all your creatures come back at end of turn)

Glen Elendra Archmage + Mikaeus, the Unhallowed / Metallic Mimic / Spark Double to allways have a counter ready

Sidisi, Undead Vizier + Mikaeus, the Unhallowed / Metallic Mimic / Spark Double (you sac Sidisi (or Spark Double) for her own ability and at end of turn she comes back because of the counter she entered with)
This way you can tutor every turn (two times per turn with Mikaeus)

Feast on the Fallen + creatures with graft / Crystalline Crawler
If you generate counters with Feast on the Fallen but all your creatures have counters allready, you can store them on creatures with graft or on Crystalline Crawler.

Tuktuk Scrapper + Spark Double for double artifact destruction (every turn if you have an sac-outlet)

Yawgmoth, Thran Physician with any graft creature to draw some cards (and shrinking your opponents creatures)

Novijen Sages + sac-outlet to draw a card for 1 mana each turn

Infinite Combos:
Mikaeus, the Unhallowed / Metallic Mimic / Spark Double + River Kelpie / Glen Elendra Archmage + Goblin Bombardment (alternativly: Flayer of the Hatebound and any sac-outlet)
=Infinite Damage (or card draw with River Kelpie. You can use it to find Glen Elendra Archmage, sac the Kelpie and Combo off while the Kelpies Persist trigger is on the stack to prevent yourself from decking. You can also use Volrath's Stronghold to put River Kelpie on the top of your deck.)

Mikaeus, the Unhallowed + Crystaline Crawler + Sac Outlet = Infinite Mana
add Flayer of the Hatebound or Goblin Bombardment for infinite Damage as well

Mikaeus, the Unhallowed + Novijen Sages + Sac Outlet (not infinite YET)
You can pay 1 to draw a card and remove the counters from two creatures to „reset“ their undying and sac them again (=card draw for 1 + two ETB/Sac-triggers)
If the sac-outlet ist Ashnods Altar you even generate mana while doing so (→ you can go semi infinite – limited only by the number of cards in your deck)
The same is true if one of the creatures you sacrifice is Dockside Extortionist.

The best Win-Cons:
Jokulhaups, Sac-Combo with Kokusho, the Evening Star/Gray Merchant of Asphodel, Infinite Combo with Flayer of the Hatebound/Goblin Bombardment
But of course stomping your opponents with counter-pumped creatures is always an option too!

Side Notes:
Graveyard hate was present in the form of Bujuka Bog, Agent of Erebos and Puppeteer Clique in earlier versions of this deck, but currently there are no graveyard decks in my meta.
In combo-heavy metas you probably want more instand-speed interaction like Chaos Warp.

Also take a look at the lower power version:
https://deckstats.net/decks/40193/2765263-marchesa-the-black-rose-lower-#show__spoiler