What was your worst misplay?

[Morganator 2.0]

I never make misplays

Oh really now?

I get hit by a Sylvan Awakening - didn't really think he'd have anything that could hit me from scratch so I was feeling confident before I lost the game to a bunch of lands. Where's the blunder? Right after losing the game I realised there was something interesting on my board - an infinite combo leading to an instant win. And it's a combo I know of, had documented and was supposed to recognise.

Aphetto Alchemist + Illusionist's Bracers + Sensei's Divining Top lets me untap the Alchemist via his own ability, effectively leading to infinite untaps for artifacts and creatures. The Top draws me all my cards when you use its ability in response to its ability and then it places itself on top of the deck. My deck would have been just the Top and casting Thassa's Oracle would have found more than enough devotion for me to win.

Needless to say it was an awful blunder, last game of the night and totally a feelsbad moment. A royal mistake.

On Mustakotka's turn they went for the win. Pay for Pact, cast Mind Over Matter, cast Archivist, equip Archivist with Lightning Greaves, use Mind Over Matter to untap Archivist to draw the whole deck and win with Thassa's Oracle.

And that would have been really cool if Lightning Greaves would gave hexproof instead of shroud. The Archivist couldn't be targeted with Mind Over Matter. MustaKotka passed and lost on my turn.

My turn. I'm excited. I count my cards: mill 12 for the Mesmeric Orb, draw 3 for Mind Unbound...and the library is empty. Draw for turn and lose the game.

[CleanBelwas]

Shots fired

[Aetherium Slinky]

I never make misplays

Oh really now?

You just did not! I don't even know what to say! Impressive. Well done.

Shots fired

B-but I just wanted to share a cool story, not try to remember something that happened two years ago.

[mynameiscalled]

I think the latest play, that is still haunting me is probably from Dominaria United prerelease. I was 2-0-1 and heading into my last game. If I win this, I'm the only player w/o defeats, and winning the whole thing. I win my first game and lose my second. We are 1-1 and in our last game; time is being called. Since this is the last game of the day and literally for first place - we play it out as long as it takes. There are quite a few people gathering to watch, I do feel it getting on my nerves a bit and I can't focus properly while I am surrounded by a circle of people whispering to each-other and whatnot. I mistake a scry 2 for this card I can't remember; it lets you look at the top two and put one into your hand. I don't draw my Sphinx of Clear Skies, instead resolve it like a normal scry. I could have cast it the same turn. End up missing last 4 dmg to close out the game next turn - opponent didn't have any flyers/ways to deal with flying. This was my first pre-release since Champions of Kamigawa - I was on a break from MTG and started playing again around 2019. I am just so mad at myself that I lost focus thanks to being on the spotlight.

[Devix]

endgame playing aurelia, the warleader vs titania.
the next turn i will close with helm of the host but in that turn i attacked with aurelia for no reason.

He had no blockers vs flying.

He plays whiteout

Blocked with a token 5/3

Loss.

[Aetherium Slinky]

Actually! I remember a recent one: I was playing a friend's deck and attacked with my The Reality Chip for funsies and got hit by a Condemn. Learnt not to do that again.

[SeraphimRisen]

I didn't notice an infinite mana combo that'd let me sac, recover, sac, recover, Noxious Gearhulk and clear the field while recovering life.

RIP.

Then later, Demonic Tutor'd a Meteor Golem instead of Nim's Deathmantle, the only piece I was missing for another infinite combo.

Both using my modified Necron Dynasties deck. Only been playing a month and a half so haven't really had a chance to make HUGE mistakes yet.

[KneeToe]

I was playing my Tuvasa the Sunlit deck, one of my friends had Enchanted Evening out. It forgot all about it really and played my Starfield of Nyx. Not realizing what I had done I was informed I murdered all my enchantment creature lands.

[LancesRoom]

I was playing a flicker deck with Ranar the Ever-Watchful, and made an infinite loop with Divine Visitation on the board, making infinite angel tokens.
I didn't have haste, so passed the turn. I had Mana up and Mana Drain in hand.

another player at the table was playing Myrkul, Lord of Bones and it's a high CMC commander, and went to cast it fo the first time in the game.
I was really considering countering it, but felt bad countering the first cast of a commander when I had such a commandimg lead.

I never expected it, but the Myrkul player won that turn with an infinite combo.

Still feels bad to think about it 🤦🏻‍♂️

[Aetherium Slinky]

I had Mind Over Matter in play. Also Folio of Fancies and Psychosis Crawler. Guess what one shouldn't do? Dump your entire hand to untap lands and then go ahead and try to activate Folio of Fancies' XX-draw ability.

EDIT: Needless to say that XX-draw was for lethal, too. (I had ~20 cards in hand and my opponents were mostly single digits.)

[UrizenII]

I accidentally played a basic Forest once.  Definitely won't let that happen again.

But in all seriousness, I misplay so often that I can't think of the worst one, just the funniest one.  EDH game with my Karlov of the Ghost Council deck.  Only two players besides me left.  I had an Aetherflux Reservoir out at 51 life.  The guy immediately before me in turn order was about to wipe the board.  I wasn't too fond of that idea, so I Death Star'd his face to take him out.  Now it's my turn.  I start my upkeep with one life... and forgot I had a Phyrexian Arena still in play.

[Lain Iwakura]

I cracked Expedition Map to complete tron, but I ended up choosing the wrong land. Do not ask me how.

[BoBWiz]

Nice thread!

Got a little story.

I played a PPTQ back in the days of kaladesh. I played grixis improvise, that was by far not tier 1 but sufficent competitive BEFORE it comes to hour of devastation. But I gave this a try again.

Cheating in The Scarab God in turn 2 or so was popular back then. I played on the draw and managed to set up metallic rebuke turn 1.

I was so nervous just forgot to cast it and (of course) lost.

It haunts me.

[crimsonking]

I once played a Stoneforge Mystic and somehow forgot to fecth Batterskull.
I mean, in my mind it was like I've had already searched my library and the Batterskull was already in my hand. I was already planning my next turn, when I'd have put into play etc. Except the search never happened, it was all in my mind. 

[Landale]

This was well over a year ago, but someone was playing a Pramikon, Sky Rampart deck and had it and a Spark Double copying it out. I go to get rid of the lockdown and use some removal. On Pramikon. Which was played again immediately on their next turn, and gave them time for Approach of the Second Sun.