Re :Zero - Starting Over in Another World has many villains, of which Regulus Corneas - Warden of Greed and Witch of Greed are the most prominent. What readers want to know is how Re:Zero: Warden of Greed was defeated because this villain has immense power.
Re:Zero: How Was the Greedy Warden Defeated?
Who is Regulus Corneas - The Defeated Warden of Greed?
Regulus Corneas is one of the Chief Warden of Sin, representing Greed. He possesses the power of the Relic “Lion's Heart”, making him an extremely dangerous opponent.

This is the character with the most outstanding power and greed. He cuts all connections between himself and the outside world to become invulnerable to magic or physical harm. The ability to stop time for a short moment allows him to perform precise and unexpected attacks.
How was Regulus defeated?
Regulus was extremely greedy and wanted everything to be his. He controlled everything from power to his wives selfishly and cruelly.
In Arc 5 of Re:Zero, Regulus, in his confrontation with Subaru Natsuki, Reinhard's weakness was found and he was defeated.
Confident with the Relic “Lion’s Lungs”, it can only protect Regulus if his heart is safe. Regulus’s fatal weakness is that his heart is outside his body, a heart shared between the wives he controls. Regulus implanted his real heart into one of his wives. But Subaru found out and lured Regulus into a protracted battle to gain time to take his real heart.

The greedy and arrogant Regulus fell into the trap because he was confident in his invincibility and underestimated his opponent. Subaru came up with strategies and Reinhard, with his overwhelming power as a Swordsman, successfully destroyed his defense mechanism, allowing Subaru to complete his plan. Subaru used his magical hand to crush the lion heart that Regulus had hidden in his wife's heart. The wife's heart was not damaged because Subaru only defeated the parasitic organ.
They freed the wives and neutralized his power.
The Greedy Warden was defeated and his end was also a great victory in the war against the Witch Cult.
Echidna - The Greedy Witch Comeback
Echidna is known as the Witch of Greed. But unlike Regulus who is very clear about his ambition, Echidna's greed is more calculated, intellectual in her desire for knowledge and control through her intelligence.
How did Echidna make a comeback?
After death, Echidna did not truly disappear. Her spirit (soul) still exists in the Temple of Trials in the Sanctuary. Subaru met Echidna in the Sanctuary during the trial. Echidna offered to help, but Subaru refused because he realized Echidna's true nature as someone who put desire and curiosity above all else.

Thus, Re:Zero: The Greedy Warden was defeated - the representative of power and tyranny but was defeated by the intelligence and solidarity of Subaru and his teammates. The return of Echidna may not be the last and plays an important role in pushing Subaru into difficult choices.