Larcade
Probably due to the nature of his magic or personality, he doesn't get much appreciation around here. I, too, admittedly have mixed feelings for this guy, so I guess I should get the personal shit out of the way first. Some people have mentioned Zeref seemingly has a prejudice against Larcade, and will meet his demise quickly once his book gets destroyed. Which I find is a lazy and half-ass way to off a character, and I'm just not a big fan of it.
Quite frankly, this guy can pose a credible threat to anyone in this competition. Larcade has some of the most outstanding feats shown by the Spriggans. It's debatable if his magic can work on someone like Wahl, but despite that, the gulf in their abilities is so huge it's not even fair.
Kagura, with her blade sheathed, has the strength and agility to successfully cut down all of Wahl's rockets in mid-air before they could do more damage. And her reflexes allow her to block and parry a sudden attack from Dimaria, when the latter does not employ her time stopping technique.
She could cut through Erza's Adamantine armour which has been capable of blocking the blast from Jupiter cannon, an attack which contributed to Ajeel's defeat.
And with her sword unsheathed, Kagura has cleaved buildings and mountain cleanly
And this same girl was spiralling into despair when she couldn't even scratch Larcade and was turn into swish kebab by nothing but his strength, reflexes and durability.
It took Sting, who could negate his technique and consuming it to replenish his energy, to unlock a new form of power after receiving Rogue's magic and assistance from Kagura's intervention, and still has to actually think and figure out a way before finally beating Larcade. Then despite his defeat, this wounded bugger still made his way to the guild in shorter time than most, and made Natsu succumbed to the effect of his magic.
His magic could also affect Zeref, Gildarts and Irene. The only realistic way of eliminating Larcade would require a level of camaraderie and teamwork which I don't see plausible with this being a battle royale, and most keen to prove their might over one another.
Gajeel
As mentioned, I will be picking my choices from what I have seen at the peak of their strength, and while I can't be bothered if that was dragon force or equivalent which Gajeel used towards the end of his fight with Bloodman, it is his strongest form that's for sure.
When considering his strength, it was devastating enough for Gajeel to tear through Bloodman's defence with physical assault. And his speed lets him unleash a barrage of repeated strikes as he outpace and pulverize Bloodman. I can believe Gajeel is rapid and powerful enough to nab a spot as one of the last four standing.
Invel
It was a toss-up between Invel and Ajeel. And I chose to go with Invel eventually.
In terms of power, both are rather similar. Invel encased Fiore in glaciers and send a blizzard raging throughout the city, while Ajeel conjured tidal waves of sand and whipped up a sandstorm that enveloped Magnolia. But where Invel has the advantage is his mentality. He is careful and confident, not cocksure of his abilities, and he has some dangerous spells in his arsenal which I find tougher to guard against as they are not your conventional attacks.
We know Ice Lock turned Gray and Juvia against each other, and despite trying to resist Invel's order, it was to no avail. The end result was Juvia committing suicide to save Gray, only averted by plot. While Ice Slave messes with one's thoughts and make them follow Invel's bidding against their will. Invel has a successful track record of pulling off these spells as they are instantaneous. And with this being a battle royale and most participants likely to have their attention and focus divided, he can bust them out anytime on his desired targets.
His power is great enough to completely dominate Gray, and even visibly nearly freeze him despite his natural resistance to cold. He did froze Natsu's fire dragon slayer magic and proceeded to freeze Natsu, Lucy, Juvia, just like he did with Mavis before, and kept them out of battle for a duration of time. There is nothing stopping him from following through his frozen targets with subsequent attacks if he truly intends to go for the kill.
Physically, he is capable of effortlessly blocking one of Gray's attacks with his bare hand. And endure being sliced by Gray's devil slayer magic attack and shrugging it off to continue fighting.
He could block the second attack from Gray, once again with only a hand.
Invel is one of the most well-balanced fighters here, so he should advance too.
Zeref
At the end of the day, despite being largely overhyped, Zeref is still one of the most powerful mages. I'm more interested to see how powerful he is now at his current state, after absorbing Fairy Heart.
