D&D 5E - The Ego Whip
If the PCs recover the weapon, would any of them actually want to use it?If a PC uses it to fight a monster, the Charisma damage is going to be irrelevant. It would take 10 hits to stun the average monster and if you are still fighting a monster after hitting it 10 times, which on average would take 20 rounds, you are doing something wrong anyway. 5e combats are not 20-round affairs, or shouldn't be.
So that leaves us with a +1 whip that does psychic rather than slashing damage, which only matters if the monster is resistant to slashing damage. There are plenty of monsters that are resistant to slashing damage from non-magical weapons but I can't off-hand think of any that are resistant to slashing from magical ones, such as a +1 whip. So it's effectively just an 'ordinary' +1 whip, which wouldn't normally need attunement, whereas yours does.
Following that line of reasoning, from the PCs point of view, it's less good than a conventional +1 whip.
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