Hapatra, Vizier of Poisons, -1/-1 Counters matter (EDH / Commander)

Deck Speed: Medium

The goal behind this mid-range deck is to deal with creature and non-planeswalker threats your opponent's pose using regular removal and -1/-1 counters. We use -1/-1 counters to make green Snakes w/ deathtouch and vanilla black Insects and green Elf Warriors to develop an army of creatures of which to attack our sorcery/instant focused opponents and to block the faster aggro strategies we come across. We run a few infect/wither creatures for no other purpose but to have creatures that put -1/-1 counters on other creatures.

The main infinite combo requires:
1.) Blowfly infestation
2.) at least two X/1 creatures on the board
3.) a token generator ( Hapatra, Vizier of Poisons, Flourishing Defenses, and Nest of Scarabs)
4.) a damage dealer ( Blood Artist, Falkenrath Noble, Poison-Tip Archer, Obelisk Spider, Vindictive Vampire ) ( Bitter Ordeal can serve as a substitute if you run into issues like Overwhelming Splendor or Humility )
5.) a -1/-1 counter source that will leave at least 1 X/1 creature alive.

With the above pieces in place, several things will occur at the same time that need to be ordered on the stack as such (with the intent on resolving in reverse order).

A.) When the counter source kills the first creature, Blowfly Infestation will want to keep the plague going by putting another -1/-1 on a creature on the board.
B.) Damage dealer deals damage to the appropriate target(s).
C.) The act of putting a -1/-1 counter triggers an effect to replace the creature that died with a 1/1 token.

For Parts B and C they can technically resolve in either order, but Part A must remain as the last part of the combo to resolve.
Since Blowfly's trigger is mandatory, it will always happen as long as a creature dies and will always restart as long as a creature dies. Because of this, we want to leave A where it is as the last thing to resolve on the stack.

If Part A is layered to resolve before the damage is dealt, we create a situation in the stack where that damage layer (and any other damage layers that we choose to resolve last for each rendition of this series) will actually not resolve as the layers of future repetitions of this combo begin to layer themselves on top of it. The same goes for the token stacking trigger.

Visual Example (stack will resolve from right to left)]
[B - A - C]
When A resolves, the combo starts again. We will layer this deck the same to ensure the combo retriggers. .
[B - (B - A - C)]

For each time that you layer the combo this way, that another set of damage that is locked away and won't resolve until the other parts of the stack above it. Even if you do find a way to break the combo, your opponents will then have a window to keep themselves from dying from a last minute life gain that will then require you to have a second source of -1/-1 counters to restart the combo