Well, literally any hard counterspell will destroy you. Even Miracles, one of the most control-heavy decks in Legacy, runs 3 Jace, 2-3 Entreat, plus a couple creatures. That's 8-9 win conditions. Running as few as 1-2 will make you sad because you will be winning until they realize how to stop you from winning.
Good win conditions in mono-black:
Sorin Markov
Corrupt/Drain Life effects
The Rack + Discard
I'm sure you can find other ways also.
Edit:
Some cards you can cut:
Phyrexian Arena - gives your opponent a 20-turn clock on you. You should expect the game to go longer. Either run a killable version or something that you can choose to activate. Perhaps Erebos, God of the Dead is what you're looking for, if you add in some gain-life effects like Corrupt and Drain Life in addition to more Tendrils of Corruption. Actually, standard all-star Underworld Connections is perfect.
Pithing Needle - Naming cards left and right is fine, but what are you going to name if you have 1-2 in your opening hand against an unknown opponent? Some Legacy decks don't even have legitimate targets with this card. Against aggressive decks like Delver, naming their fetchland will neither work nor solve the problem of the 3/2 flyer beating in your face. This is good in the sideboard or as a 1-of tutor target if you increase the Beseech the Queen count. I have tried getting people with this many times, and it is not effective enough.
That's 6-7 cuts, so in addition to the Elixir/Haunting Echoes package that you can cut, you now have 8-9 slots for real win conditions.
How dedicated are you to the creatureless bit? There are some really, really good creatures that you could run in a MonoBlack deck. I understand not wanting to shell out for Dark Confidant in a budget deck, but guys like Gatekeeper of Malakir are nice to have around.
Check out "The Gate" in the deck section, it's probably the closest to a competitive MonoBlack deck.
Budget "Pox" is often creaturless and for about $100 you can build it easy; possible less. For example:
4 Smallpox
3 Pox
3 Cursed Scroll
4 The Rack
would be enough to easily kill many opponents fairly quickly. Even just swapping your list with some Cursed Scroll and other damage effects would be good. Ankh of Mishra with Bloodchief Ascension is fun and with Scroll it can easily get active; in which you're draining the opponent with every card you can hit via discard or kill.
4x dark ritual
1x Drown in sorrow
3x Duress
1x Disfigure
1x Elixir of immortality
1x extirpate
1x Haunting Echoes
4x Hymn to tourach
4x innocent blood
1x Oblivion Stone
4x Phyrexian Arena
3x pithing needle
2x Sadistic Sacrament
3x Sign in blood
23x Swamp
1x tendrils of corruption
1x toxic deluge
1x zuran orb
Legacy:
GRISELBRAND
Good win conditions in mono-black:
Sorin Markov
Corrupt/Drain Life effects
The Rack + Discard
I'm sure you can find other ways also.
Edit:
Some cards you can cut:
Phyrexian Arena - gives your opponent a 20-turn clock on you. You should expect the game to go longer. Either run a killable version or something that you can choose to activate. Perhaps Erebos, God of the Dead is what you're looking for, if you add in some gain-life effects like Corrupt and Drain Life in addition to more Tendrils of Corruption. Actually, standard all-star Underworld Connections is perfect.
Pithing Needle - Naming cards left and right is fine, but what are you going to name if you have 1-2 in your opening hand against an unknown opponent? Some Legacy decks don't even have legitimate targets with this card. Against aggressive decks like Delver, naming their fetchland will neither work nor solve the problem of the 3/2 flyer beating in your face. This is good in the sideboard or as a 1-of tutor target if you increase the Beseech the Queen count. I have tried getting people with this many times, and it is not effective enough.
That's 6-7 cuts, so in addition to the Elixir/Haunting Echoes package that you can cut, you now have 8-9 slots for real win conditions.
Legacy:
GRISELBRAND
Check out "The Gate" in the deck section, it's probably the closest to a competitive MonoBlack deck.
http://www.mtgsalvation.com/forums/the-game/legacy-type-1-5/178367-getting-started-in-legacy-and-legacy-budget-primer
I really suggest you check them out, as they follow pretty much exactly what you want, and what others have been and are likely to suggest to you.
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4 Smallpox
3 Pox
3 Cursed Scroll
4 The Rack
would be enough to easily kill many opponents fairly quickly. Even just swapping your list with some Cursed Scroll and other damage effects would be good. Ankh of Mishra with Bloodchief Ascension is fun and with Scroll it can easily get active; in which you're draining the opponent with every card you can hit via discard or kill.
Look, Fetch, Draw, Look
Draw
Fetch
Look