whose the most difficult wild Pokémon you've ever encountered

Dragonite....pre Gen2
He took 70+ balls before fleeing

Charizard during the starter event. 30-40 ultraballs and razz berries. level 28 E/FT

Charizard without any doubt for me, two encounters, the first one some months ago, a lot before gen2 released, I had only two blank spaces on my dex, Charizard and Lapras, I ran like a crazy when I saw Charizard shadow on my nearby and found him next to a small road where two cars were parked trying to get him.

It took exactly 69 ultra ball with rasp to get him, was the hardest fight I have ever had with this game, around 20-30 minutes, I ended up exhausted. I remember that I got like more than 60% of the throws landing a great but still he did not want to come with me. Finally got him on the 69th ultra, he ate 80% of the ones I had saved at that point, but worth it for the dex entry. Of course his IV were the most crap ever, something like 10% or so lol.

The second one, again Charizard, during the starters event, again bad IV, 32 ultra with rasp before I caught him. Not a single mon has put that of a fight to me a part from Charizard, not even Dragonite, he runs or catches a lot quicker, I have seen 3 Dragonites, 2 run, 1 captured, all of them stayed for less than 10 balls, but Charizard wow, that mon is a fighter hahah xD

Surely that was a glitch. I will never pay for Poke balls while escape and flee exist in the game.

Stop wasting our time and resources Niantic.

Togetic when Gen 2 first launched. I don't remember exactly how many balls, at least 80-90 and I ran thru 40+ razz berries. I believe I only caught it because of Critical Catch. Or else it would have ran away like all the other ones when Gen 2 was first launched.

Dragonite, Charizard, Lapras (before the throw mechanics changed) used to suck up lots of Ultras.

Recently Togetic when Gen 2 was launched, it was pretty much impossible to catch because its Base Capture Rate was like, 1% or something impossible. However, since they increased the BCR I've caught a couple without issues.

Dragonite definitely! At the start of gen one they could be insanely hard to catch..

U guys are kinda scaring me. I rarely have more than 30 ultraballs at a time and if i do its just a few more. I often run out of pokeballs and cant stock up that much since i can only do it from time to time when i go to a big city for some reason. Do i have to start choosing what i catch after lvl 30 (27 here) instead of just catching everything like ive been doing in case one of those enconters occur? Or even worse do i have to not catch anything at all for a while to keep the pokeball numbers high?

My first Dragonite, who fled after many ultra balls and red berries.
And first wild rapidash, couldn't reach it with balls, it was too far, so I run away.

I haven't encountered many super hard mons that some of you guys encountered, but I'll probably give the cake to either Charmeleon (I haven't encountered a wild zard) or a level 30 Sudowoodo. The 2106 CP wild vaporeon was pretty hard too.

Fun points:
My first Dragonite was a one shot catch (though it was 747 CP lol)

My first Lapras was a one shot catch (2212 CP back in the day, now 1927)

My first Snorlax was also a one shot catch (225 CP lol...)

togetic could have been pre adjustment but i recognized the futility and couldn't afford to continue after 10

charizard pre gen 2 50 balls and berries then gave up.

Lapras. Took like 30 ultras since it was my first and I was panicking, though most of them were missed throws since I had trouble throwing them far enough.

This was back in November i think, it seems since gen 2 some Pokemon aren't as far away anymore.

Muk and Venusaur. Didn't keep count, but I used a lot of balls and berries.

Most of the time, if I don't catch something pretty quickly I'll just leave it and not waste the resources unless I really want it. Items are always low for me living in a rural area. I try to stock up when I'm at work, but sometimes I don't always have the time.

Kabutops? Just several minutes ago. Didn't waste many balls and berries though, it just fled.

The ones the stand out in my memory:
three Charizard, a Togetic, and any Murkrow over about 600 CP.

The one that stands out the most in my mind was a Scyther, months ago. That wasn't because it kept breaking out, but because no matter what I did, 80% of the throws just would not reach it. Throw after throw after throw, from the very bottom of the screen to the very top, each ball would just land on the ground in front of him. And then the rare ball that did actually go far enough, the Scyther would dodge every time. I tried 20 or 30 times, about 10 with ultra balls, then when I finally hit it once and it broke out anyway, I just gave up. I was so glad when one update moved many pokemon closer to the screen, so they weren't so impossible to reach anymore.

Before that, Gengar gave me a lot of trouble during the Halloween event. I was only something like level 10 at the time, didn't know about curve balls or hitting the accuracy circle, and since I only had normal pokeballs, they just broke out every single time. I never did manage to catch one, and just found the event annoying because it made me throw away all my items for nothing.

I also had one Murkrow that was a real pain. I had a lucky egg going, and I was trying to get my first-catch-of-the-day bonus, but it just kept breaking out, throw after throw after throw, the only Murkrow that's ever given me anywhere near that much trouble. Usually I just toss a few regular balls at Murkrow, and even if they're high CP, I'll either catch it or it will run away within 3 or 4 tries, but this one took like 20 and wasted a good chunk of my lucky egg. After I caught it, I named it Time Waster, killed it in a gym, and tossed it in the trash.