Just need a clarification about the powerful build with the warforged counting as one size larger, does that mean I could use a two-handed weapon in one hand?

Fair enough. I interpreted that as for example, an ogre is one size larger and can carry a great club in one hand so that means he could. A good rule of thumb to know either way.

To clarify, the Ogre is using a large greatclub two handed. If you were actually size large (like with enlarge), you still couldn't use a greatclub one handed RAW. You could use a large club one handed that would do more damage than a medium club.  The net effect is roughly the same and I would personally allow a large character to use a normal two handed weapon one handed, but it's not officially allowed.

As Stormknight said, 5e (thankfully) simplifies the weapon / creature size issue considerably. The key points being:

• Small creatures have disadvantage on attack rolls with heavy weapons. That's any weapon with the 'heavy' property, such as greatswords.
• Oversized weapons meant for creatures one-size larger than the player can be wielded, but with disadvantage on attack rolls.
• With oversized weapons, you double the damage for large, triple for huge, and quadruple for gargantuan.
• The DM can rule that you cannot use a weapon meant for a creature two sizes larger than you.

And that's pretty much it. There's no rules or feats for wielding two-handed weapons in one hand if you're a size larger or anything. The only weapons that can be used in either one or two hands are those with the 'Versatile' property. And that has nothing to do with size.

Quote from Chequers >>

As Stormknight said, 5e (thankfully) simplifies the weapon / creature size issue considerably. The key points being:

• Small creatures have disadvantage on attack rolls with heavy weapons. That's any weapon with the 'heavy' property, such as greatswords.
• Oversized weapons meant for creatures one-size larger than the player can be wielded, but with disadvantage on attack rolls.
• With oversized weapons, you double the damage for large, triple for huge, and quadruple for gargantuan.
• The DM can rule that you cannot use a weapon meant for a creature two sizes larger than you.

And that's pretty much it. There's no rules or feats for wielding two-handed weapons in one hand if you're a size larger or anything. The only weapons that can be used in either one or two hands are those with the 'Versatile' property. And that has nothing to do with size.

 

 I've been looking for information like that! For some reason, I'm not remembering seeing those points in the RAW anywhere though. Do you know where I can find them?

Quote from Faltyn >>

Quote from Chequers >>

As Stormknight said, 5e (thankfully) simplifies the weapon / creature size issue considerably. The key points being:

1. Small creatures have disadvantage on attack rolls with heavy weapons. That's any weapon with the 'heavy' property, such as greatswords.
2. Oversized weapons meant for creatures one-size larger than the player can be wielded, but with disadvantage on attack rolls.
3. With oversized weapons, you double the damage for large, triple for huge, and quadruple for gargantuan.
4. The DM can rule that you cannot use a weapon meant for a creature two sizes larger than you.

And that's pretty much it. There's no rules or feats for wielding two-handed weapons in one hand if you're a size larger or anything. The only weapons that can be used in either one or two hands are those with the 'Versatile' property. And that has nothing to do with size.

 

 I've been looking for information like that! For some reason, I'm not remembering seeing those points in the RAW anywhere though. Do you know where I can find them?

1. "Creatures that are Small or Tiny have disadvantage on attack rolls with heavy weapons. A heavy weapon's size and bulk make it too large for a Small or Tiny creature to use effectively." (https://www.dndbeyond.com/sources/basic-rules/equipment#WeaponProperties)
2. "A creature has disadvantage on attack rolls with a weapon that is sized for a larger attacker." (https://www.dndbeyond.com/sources/dmg/dungeon-masters-workshop#CreatingaMonsterStatBlock)
   
3. "Big monsters typically wield oversized weapons that deal extra dice of damage on a hit. Double the weapon dice if the creature is Large, triple the weapon dice if it’s Huge, and quadruple the weapon dice if it’s Gargantuan." (same source as 2.)
4. "You can rule that a weapon sized for an attacker two or more sizes larger is too big for the creature to use at all." (same source as 2.)

Quote from Emmber >>

3. "Big monsters typically wield oversized weapons that deal extra dice of damage on a hit. Double the weapon dice if the creature is Large, triple the weapon dice if it’s Huge, and quadruple the weapon dice if it’s Gargantuan." (same source as 2.)

 Note that this is the rule for creating a creature, it does not mean that a PC that increases in size automatically gets to double their dice (you just get what the feature says you get). For example, being enlarged via Enlarge/Reduce gives you +1d4 in damage dice.

Thank you for the cites! I appreciate it!

Quote from Thezzaruz >>

Quote from Emmber >>

3. "Big monsters typically wield oversized weapons that deal extra dice of damage on a hit. Double the weapon dice if the creature is Large, triple the weapon dice if it’s Huge, and quadruple the weapon dice if it’s Gargantuan." (same source as 2.)

 Note that this is the rule for creating a creature, it does not mean that a PC that increases in size automatically gets to double their dice (you just get what the feature says you get). For example, being enlarged via Enlarge/Reduce gives you +1d4 in damage dice.

 thank you for pointing this out. I see waayyyyy too many players cite the NPC creation rules for PC abilities and I'm like "stay out of my dmg please" lol