Shunning Miser
Creature - Human Cleric
Players can only cast one spell each turn.
Whenever an opponent casts a spell, that player loses 1 life and you gain 1 life.
"Fool me once, shame on me. Fool me twice . . . well . . . I'll make sure there isn't a second time."
[1/3]

This feels antisynergistic with itself. Like, it's already punishing them for casting multiple spells per turn.

this is true if you view it as mainly the second ability, but I think it's better viewed as being mainly about the first, with the second as an extra little stab if they try to even cash in their one allotted spell, and from that lens I think the synergy works fine.