Around 1300 tma just similar to bishop if you maxed meteor shower and are using a fire elemental wand. Note that 1hit threshold varies with the amount of int you have so it could be a few tma higher/lower than 1300. Maxing meteor shower is way cheaper than maxing genesis since the books are cheaper. But I assume you want to 1hit to sell leech or self-leech, so you likely want to have hs. This means you either want to have a bs or have a fp with a hs mule on the side.
That doesn't seem correct... unless I'm missing something? Holy Damage (i.e Genesis) does 50% bonus damage to skeles. Fire Damage (i.e Meteor Shower) does not have any bonus on its own. But with a fire elemental wand, it does 25% bonus damage. And according to this source, Genesis has higher base damage than Meteor Shower (670 vs 570) https://royals.ms/forum/threads/mapleroyals-skill-library.209540/ So I don't think you can simply swap one for the other and expect the TMA to remain approximately the same.
Ur missing element amplification from 3rd job which gives 140% dmg boost. I sold skele leech with 1300 on my fp and had no issue with it
With elemental boost it's 148% (F/P) vs 150% (bishop). So bishops will just barely outdmg F/P and I/L
I/L / F/P need around 1315 TMA to 1 hit skele (exact number depends on the total int). The main advantage of a bishop is that you got hs and dont need a mule
calculation has been discussed above (BS 1.5x elemental weakness 670 base attack / ArchMage 1.4x skill boost 1.25x wand bonus 570 base attack) I will just back up with my own experience I/L mage lv around 145-150, All AP used on INT need 1306 magic to 100% 1hit (1305 will bring ~0.5% chance of not killing in 1 hit)
this doesn't mean much, it still depends on the total int you got (including the int from gear). at level 150 assuming you got 900 int (should be pretty easy with mw20 and gear), you would need 1310 to 1h skele. It is just math to know exactly how much tma is needed.