Is RA the most powerful god card?
The Winged Dragon Of Ra
Considered to be the most powerful of all of the Egyptian God cards, The Winged Dragon Of Ra being summoned makes for some epic moments in the anime. The attack and defense points for it are made up of the total of the three cards you tribute for it.
The legal OCG/TCG version of "Ra" is arguably the strongest and the weakest Egyptian God due to its own effect. If you do pay LP when you Normal Summoned it, it can have a very high ATK & DEF, especially if you managed to Summon it early in the duel, at the cost of you having only 100 LP left.
They can be destroyed by Trap Cards that target (in the anime, "Blast Held by a Tribute" destroyed one monster and inflicted damage based on its ATK, so it targeted). They can be affected by targeting Traps ("Magic Cylinder" and "Spellbinding Circle").
All 3 Egyptian gods are available and are limited to 5,000 worldwide, each card is individually numbered making it unique and very highly collectable.
As a result, the Winged Dragon of Ra is played up as being stronger than Slifer.
It's a tie. Exodia's lore says he has infinite power and is so powerful he is trapped with a seal and is seperated into 5 parts whereas Ra, you just have to say it's ancient text to summon it. But it's a close call because most of Ra's ancient power is unknown.
I think that Slifer is probably more favored with the new structure, but Obelisk is still superior and could prevail with his deck.
Goku stated that Ra is as powerful as Shido in his Omni-King state and possess abilities that far exceeds any gods such as the Gods of Destruction and the Harmony Gods. His power level is about 1,226,500,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000.
Exodia *requires* all five cards to be in hand in order to unleash him. That being said, Exodia eclipses the God Cards by virtue of being an automatic victory, able to wipe the field like Obelisk *and* wipe life points out in one move.
Summon this card using "Hardened Armed Dragon" to protect it from destruction by card effect.
Why are the god cards weak?
In terms of the anime, the God Cards have been made weaker due to new mechanics added to the game. At the end of the original series, Yugi was able to defeat all 3 at once.
If they're playing Trap Stall Exodia, Royal Decree and Trap Stun will kill them. When they're relying on Battle Fader or Swift Scarecrow to block attacks, negate them with Solemn Strike, etc, or prevent them from activating entirely with a card like Utopia the Lightning, Armades, or Odd-Eyes Meteorburst Dragon.

Conclusion. Ra as the unseen power behind all other powers extended to every god in the Egyptian pantheon.
franchise has likely heard of the legendary Blue-Eyes White Dragon. It is the strongest regular Normal Monster in the game and an icon known as a bringer of destruction. It is the favorite card of Seto Kaiba, who uses his 3 Blue-Eyes to reign devastation upon his foes as often as he can.
The Ace of Spades (also known as the Spadille and Death Card) is traditionally the highest and most valued card in the deck of playing cards in English-speaking countries. The actual value of the card varies from game to game.