Moves that have low power should be low power

[ress1n]

Something like leechlife should not be capable of getting a 1 hit KO when its used by a pokemon that is almost 10 levels lower than the one its battling, even if it is super effective its makes no sense for it to 1 hit KO.

[CaptnBaklava]

Isnt leech life like 80 base power?

[Rache]

Leech Life has 80 power here like it does in gens 7 and 8. The damage calculations are as close to the original games as possible, there's nothing wrong with the situation you're describing when it's something with high attack hitting something with low defense. You can confirm how much damage a move should be doing here.

[hannahtaylor]

1 hour ago, CaptnBaklava said:

Isnt leech life like 80 base power?

It is, yes

[Rakhmaninov]

2 hours ago, ress1n said:

Something like leechlife should not be capable of getting a 1 hit KO when its used by a pokemon that is almost 10 levels lower than the one its battling, even if it is super effective its makes no sense for it to 1 hit KO.

PokeMMO uses the Generation 8 base power for all moves, as far as I'm aware, which means leech life (as CaptnBaklava rightly said) has 80 base power. 

Use the latest Pokemon Damage Calculator to see how much damage moves do :)