There is a nearby divination wizard who rolled a 20 this morning. He gives the attack a 20, so it hits anyway.

I cast True Strike

You strike true, cutting down a young hero in their prime with your blade. An angry mob hunts you down and tears you to shreds as punishment. Later, the kingdom is destroyed by the sea monster that hero was destined to defeat.

I cast Blink. 

You accidentaly blink into the nine hells instead of the ethereal plane and are obliterated by Asmodeus.

I cast Otto's irresistible dance

people barf and gag as they can't unsee your "irriestible dancing" because your a Pustuloid. (might want to google that homebrew for visual referance)

I cast Jump

You triple your jump distance, bringing it to a high enough total to clear a ravine. However, your DM forgets that the jumping rules for D&D exists, and calls for a check even though this jump should be effortless for your character now. When you remind your DM that those rules exist, he tells you to stop being so "muddled down in the rules" and tells you once again to roll athletics. You roll low, and fall in.

I cast Power Word Kill.

sadly, the target has 101 hp

I cast invulnerability

Sadly, you have 100 HP. I cast Power Word Kill again.

Then, I cast Destructive Wave.

The wave is so destructive that it destroys everything but your intended target

I cast Ice Knife

You cast the spell as normal, and everything seems fine, at least at first. Then, a passing ClerciPure™ agent realizes that, if the knife is later melted, it could be used to duplicate their product, which is still protected by a patent. The case reaches the Neverwinter supreme court. The question is: does ClerciPure have the right to suspend all water spells for everyone but themselves? I guess we'll find out soon.

I cast Skywrite.

The clouds condense into water and ClerciPure(TM) gets mad.

I cast alarm

@Panda_wat, how did you get the superscript TM? When I tried using  tags it would work in the editor, but not when actually posted.

You cast alarm which turns out to actually be a signal for ClerciPure(TM) agents that seek to protect their valued patent and you are swiftly brought to an underground dungeon. 

I cast Produce Flame

ClerciPure(TM) sees your Flame production as competition and a serious threat to there water productions! There now gunning for you

I cast Animate Dead

Quote from VitusW >>

@Panda_wat, how did you get the superscript TM? When I tried using  tags it would work in the editor, but not when actually posted.

 

I have a "special characters and emojis" system on my OS.

Quote from EarthChip2888 >>

I cast Animate Dead

There is a nearby 5th-level cleric who immediately uses Turn Undead, destroying all of the low-level grunts you just made, then calls down a Holy Smite of Smiting upon you for being a horrid sinner. Why that spell is on the cleric list is beyond me.

I cast Prismatic Wall.

You trap yourself in the wall.

I cast Hunger of Hadar

Hadar gets hungrier than normal, and you're looking like a delicious snack right now. Run.

I cast True Strike. Good luck worsening the worst spell!

You roll the dice. A 1 and a 20. Thank the dice! They have come through with you today and you have slain your enemy with the 20... oh wait. What's that the DM says? That was an NPC meant to give you crucial info? Info that would make the next stage of the quest vastly easier? And now not only have you lost that info but turned the whole kingdom against you? ...whoops.

I cast Power Word Kill

Yeah, I've got 101 HP.  :-) 

I cast Dark Star

The sun goes out, leaving the planet cold and dead.

I cast weird.

You're weird.

I cast PRESTiDIGITATIoN

You're accused of witchcraft and found to weigh less than a duck. 

I cast Minor Illusion