Grimble then quintus.
dont forget to feed some kunchen to them in the process!
Maybe tell us a little bit more , what would like to use the hero for the most? Raid defense, war team , offense or titans? 
Some screenshots of your already ascended heroes could help. 
Guardian Panther for certain.
What a nice roster.
Panther will be beneficial since u alredy have many max purple
Panther 100% you can’t go wrong in this
That’s what I’m leaning towards Clarissa is new was just trying to get a little feed back
After seeing your great roster, Panther will my choice. Her elemental debuff is a must. Amazing against holy heroes and titans.
I faced a similar conundrum sometime back between giving tonics to Evelyn and Lianna. Drawing from that experience, let me present you my thought process:
What level of titans does your alliance face consistently? 6, 7, or even 8* titans? Guardian Panther at 3/70 usually works fine for that level. Go for Clarissa.
Guardian Panther’s main role is to cast the elemental debuff (which she does just fine at 3/70) and enable the rest of the purple heroes to do maximum damage.
Essentially, I guess the real question here is “Does your Panther get one-shot killed by the titans you face?”
If yes, then ascend Panther. Her survival is important.
If no, you can work on Clarissa (as Panther is doing her job just fine, while Clarissa needs to be maxed to bring out maximum utility from her.)
Just my 2 cents!
A great and well thought answer.
I would lean toward panther because despite titan I would throw in event and pve content.
A mono purple team with kunchen panther ursena hel rigardcostume can beat any event stage (except purple reflect) in great times and no chance for bosses to gain mana.
Also kunchen+panther+kageburado is a save pvp kill. And panther also dispels 3 targets what can be so very useful.
Probably @Kreeves you should also check if you do have enough purple mana troops to bring both kageburado and clarissa to 6 tiles. It tremendously strengthens very fast heroes.
Damn, why do you pull so much?! With the lack of game modes in this game, when are you even going to use all those 5* heroes? Seems like a waste to me 
Anyways, I’d say Panther because she boosts your other purples to incredible power and is wonderful for offense
Panther is the most universal hero (War, Events, PVP etc.) from your possible candidates = you will have the major effect from your mats.
As the others said you already have a lot of good purple heroes - a lot of them emblemed - and they will get boosted from Panther.
Clarissa is nice but with you actual roster depth more a luxury choice than a reasonable one.
Elemental def heroes are always most important, Panther first.
I agree, an elemental debuff hero is an important addition to your team in all aspects of the game. I’d max Panther first.
Similar situation, but not with the depth of Kreeves’ roster. Clarissa and Panther sitting at 3/70, my maxed purples include Seshat +9, Ursena +4, Kunchen just finished leveling, Rigard +12 (costume 3/56), Proteus +4, Sabina +4, Tiburtus +0. Looking mostly for Titan, AW and raiding help. I also have Sartana and Kageburado at 1/1 (just picked him up). Leaning toward G. Panther, our alliance is mostly hunting 6-8 (we have yet to take down an 8* Titan).
Gotta get 'em all!
20 complete rosters