Forcing Constitution save penalties?

[ES Curse]

Basically, what player options/features can be used to weaken an opponent's Constitution saves? I've been thinking about a poison-themed character for a while now and noticed that the key to poisoning someone is having them fail a Constitution save. What are some ways to accomplish this?

[Foxhound438]

-bane (spell)

-bend luck (sorcerer ability)

-heighten spell (sorcerer metamagic)

-eldritch strike (fighter ability)

-contagion (spell)

those are the only things I can think of off the top of my head.

[TheFlyingCleric]

That list above, as well as:
- Bestow Curse (spell)

[Grod_The_Giant]

The Diviner's Portent, portentially.

[Flashy]

There's also the Arcane Trickster's Magical Ambush.

[Seekergeek]

Also, Hex.

Nope, nevermind. Was temporarily AFB. And also wrong.

[Aldarin]

The Diviner's Portent, portentially.

That was a good one