Tynranitar dilema

Well, I can talk for myself, but my favourites and the top tier mon I get with a 100% IV are an instant evolve and power up to the max. Have done it with Tyranitar (from a raid), Gyrados, Rhydon and Vaporeon.

And also have done it with not top tier but personal favourites, like Poliwrath and Blastoise.

With that being said, rare candies for me are only useful for legendaries, the rest of candies you can get from catching, hatching and walking as a buddy and in the future you may regret spending all that rare candies if you get a high IV Zapdos, Mewtwo, etc...and you don't have enough of them to max it out.

Do what you most like, but keep in mind rarity and utility of the different mon.

Ah - the logic/efficiency vs pride conundrum...

Two immediate options come to mind:
1) Keep raiding Ttars until they rotate, maybe you will nab another 100%? At least you will accumulate more Ttar candy....
2) Make him your buddy and a long-term project - take 100% pride in a perfect hatch and earned candy!
A First World dilemma!

Yeah, I personally would never use rare candies for mons which you can hatch, catch, pinap in the wild...

You already have 3 Tyranitars, but can make the 100% your longer term project and just keep walking/hatching/catching Larvitars and when you get enough, you can power it and max it out then...I'm lucky that I can catch Larvitar's in the wild in my area (Desert and don't use maps, but NEVER a Dratini or Magikarp)...

I had over 500+ Larvitar candies (7 hatches, some double candies) before I even got my 1st Tyranitar (evolved) so in all honesty, I don't really see or have a need to "rush" to either complete the dex or evolve/power up any mon...

It feels great though, for my own game that I can max anything out if I want (always keep a stock of dust) and still have 300+ Larvitar candies...Just need more candidates to power up.

You can do well enough in the game without having optimal everything.

TL:DR - I'd keep walking/hatching Larvitars and just keep the 100% Larvitar as a long term project...Power up the 95% if you need to use one for Mewtwo.

Ya I'm kinda torn too, my 1st instinct is to evolve that bad boy but if you got a couple of 95s ya I would just make it a long term project. I know once I evolved my 100 Gyarados I pumped everything I had into it. Kinda lost his luster now but he is a beast in battle.

If it were me, I'd do it, it is 100! I'd feel obligated.

I can't add much more except my experience. I too hatched a perfect larvitar and had only 80 larvitar candies. I went ahead and used about 100 rare candies to evolve and power that beast up to around 3000. Going forward, I'll slowly max her out without using any more rare candies.

In the long run, this is the right move versus powering up my other Trex's although the most prudent thing would have been to wait until I got enough larvitar candies. That being said, I still have 130 left for my 1888 Zapdos and beyond.

Rare candies are easier to come by than larvitar candies where I live. If they end up releasing more legendaries soon, then I'll just have to grind it out.