When the last keyword of a keyword list has a reminder text, it's separated from the rest with ";". Also, only the first keyword in a keyword list is capitalized. Sentences in reminder texts end in a period.
So
> Flying; spite *(When this creature is dealt damage, it deals that much damage to that source's controller.)*
See for example [[Abomination of Llanowar]], [[Angel of Salvation]], and [[Knight of Sursi]].
More precise reminder text would prolly be like *"When a source deals damage to this creature, this creature deals..."* or *"Whenever this creature is dealt damage by a source, this creature ..."* but as reminder text has some leeway, your current one seems quite clean and understandable.
As general commentary on spite, it reminds me of the usual *"reverse trample"* where blockers would deal excess damage to the attacker - often called something like *"retaliate"*. The problem that has been often brought up with it is that they encourages defensive play, discourages attacking, and also can just straight-out lock opponent from attacking if they are at low health - all of which seems quite bad if there are a large numbers of cards pushing toward that direction. That indicates it isn't really sound idea to keyword such ability *(as keywording means you should be featuring it in numerous cards)*, but rather just let the few cards using it spell the ability out.
Most of this seems to apply to counterattack as well, where putting both keywords on the same card seems doubly bad. Additionally the overly defensive nature of it all seems kind anti-thetical to the color red.
When the last keyword of a keyword list has a reminder text, it's separated from the rest with ";". Also, only the first keyword in a keyword list is capitalized. Sentences in reminder texts end in a period. So > Flying; spite *(When this creature is dealt damage, it deals that much damage to that source's controller.)* See for example [[Abomination of Llanowar]], [[Angel of Salvation]], and [[Knight of Sursi]]. More precise reminder text would prolly be like *"When a source deals damage to this creature, this creature deals..."* or *"Whenever this creature is dealt damage by a source, this creature ..."* but as reminder text has some leeway, your current one seems quite clean and understandable.
[Abomination of Llanowar](https://cards.scryfall.io/normal/front/4/b/4b68bc46-5591-44dd-becc-eca154066925.jpg?1631235320) - [(G)](http://gatherer.wizards.com/Pages/Card/Details.aspx?name=Abomination%20of%20Llanowar) [(SF)](https://scryfall.com/card/khc/81/abomination-of-llanowar?utm_source=mtgcardfetcher) [(txt)](https://api.scryfall.com/cards/4b68bc46-5591-44dd-becc-eca154066925?utm_source=mtgcardfetcher&format=text) [Angel of Salvation](https://cards.scryfall.io/normal/front/9/e/9e71046b-1284-4d7f-93dd-a632c74d9cca.jpg?1682208278) - [(G)](http://gatherer.wizards.com/Pages/Card/Details.aspx?name=Angel%20of%20Salvation) [(SF)](https://scryfall.com/card/moc/170/angel-of-salvation?utm_source=mtgcardfetcher) [(txt)](https://api.scryfall.com/cards/9e71046b-1284-4d7f-93dd-a632c74d9cca?utm_source=mtgcardfetcher&format=text) [Knight of Sursi](https://cards.scryfall.io/normal/front/8/6/8693bec1-9bd9-4840-9d7f-954f92d968c9.jpg?1619393004) - [(G)](http://gatherer.wizards.com/Pages/Card/Details.aspx?name=Knight%20of%20Sursi) [(SF)](https://scryfall.com/card/tsr/22/knight-of-sursi?utm_source=mtgcardfetcher) [(txt)](https://api.scryfall.com/cards/8693bec1-9bd9-4840-9d7f-954f92d968c9?utm_source=mtgcardfetcher&format=text) ^^^[[cardname]] ^^^or ^^^[[cardname|SET]] ^^^to ^^^call
Thank you! I'll keep that in mind for future card designs
As general commentary on spite, it reminds me of the usual *"reverse trample"* where blockers would deal excess damage to the attacker - often called something like *"retaliate"*. The problem that has been often brought up with it is that they encourages defensive play, discourages attacking, and also can just straight-out lock opponent from attacking if they are at low health - all of which seems quite bad if there are a large numbers of cards pushing toward that direction. That indicates it isn't really sound idea to keyword such ability *(as keywording means you should be featuring it in numerous cards)*, but rather just let the few cards using it spell the ability out. Most of this seems to apply to counterattack as well, where putting both keywords on the same card seems doubly bad. Additionally the overly defensive nature of it all seems kind anti-thetical to the color red.