Here's my story about unfairness in customs:
I used to play a card that could halve my opponent's life points by banishing itself (a
Synchro Monster). People were often ranting that it was broken, can't halve for free, etc. At that point i did agree with them, so i removed the monster.
Days later i created another custom card, for the people in customs, main menu, discord servers (in general) was broken, even though it was an upstart goblin that drew a card once per duel. Alright.
At this point i said: "Hmm.. maybe i could play the TCG/OCG game to get an idea of what is broken and what is not" <----- This was the enlightenment.
· I activate
Solemn Warning, opponent? you don't let me summon my monsters, how i'm supposed to play?, rage quits.
· I activate
Skill Drain, opponent? says the whole game is about monsters' effects & proceeds with a little "screw you", rage quits.
· I activate
Ash Blossom & Joyous Spring, opponent? rants about that being an unfair card, he's now starting with 4 cards in their first turn, rage quits.
I decided to change my deck, from control to beatdown.
Opponent: I hate the OTK decks, they're not fair to play against, you win in 1 turn, you're a noob.
Alright, i change my deck to stall (exodia).
Opponent: You're not fun to play against, bye. Quits.
Then i played an aggro deck.
Opponent: You Special Summon way too much, how many summons was that? 30? *rage quits*.
Finally i decided to use a
Vanilla Deck.
Opponent: You're a noob, get some real cards to play LOL your deck is lame.
Me in my mind: (Real cards for you to rage quit?.. lulz)
At the end you realize is not about the cards, the effects, is about the player. For example you can consider something in customs broken, while konami releases cards like Engage (+7 per turn), SPYRAL Master Plan same (+7 per turn but unlike Engage, with master plan you only need her and Quick-Fix), Dragun of Red-Eyes? there are people praising that card saying its a fair card, "shouldn't be banned". You can see the hypocrisy in most players.
I suggest you to make your cards as you want, with common sense you'll eventually find out what is balanced or not. Don't ask anyone in duelingbook about balancing effects. And for god's sake, don't join the "Custom Cards Format" server (CCF), they have poor understanding about Yu-Gi-Oh! cards. Join the Shadow Realm server instead
https://discord.gg/3aVGFt.