How to unlock Yveltal
Yveltal is not sold directly, so the only route is the Kalos banner, where it occupies a 5★ slot. The 5★ band takes 1.5% of all pulls and holds 103 partners, so one specific Yveltal works out to about 0.0146% per draw. The 70-pull pity counter guarantees a 5★, but it does not target Yveltal specifically, so a guarantee can still resolve to another 5★. A duplicate Yveltal refunds 300 coins at the 5★ rate.
Yveltal stats and rank
Yveltal reads 127 HP, 120 speed, ×1.42 attack, ×1.42 physical, ×1.42 special, 95 defense and 98 special defense, for a 680 base-stat total. On the three-stat percentile this is 90.8 out of 100, which puts Yveltal at rank 12 of 966 and in tier S. The relative picture matters more than the total: its strongest slot is HP (97th percentile) and its weakest is defense (79th percentile), so it spreads its value fairly evenly.
Best moves in Yveltal's pool
At move level 5 the pool is led by Gust at 31.2 damage per 0.26s (170.6 effective DPS, ×1.42 multiplier), then Body Slam at 75.6 damage per 0.71s (150.7 effective DPS, ×1.42 multiplier), then Bite at 35.7 damage per 0.34s (150.2 effective DPS, ×1.42 multiplier). 10 of its 17 damaging moves scale with the physical multiplier and 7 with the special one, alongside 4 support moves. Its physical and special multipliers are identical at ×1.42, so the pool decides the build. The top option beats the second by 19.9 DPS, which decides slot one and leaves slot two as a judgement call. Range, area and knockback are not in the DPS number, so a nova can beat a melee on clear speed despite a smaller figure.
Evolution cards for Yveltal
Its starting move, Bite, evolves into Crunch once the move is at level 5 and you hold the Power card, which boosts attack for that run. If Power never appears in that run's level-up offers, the move stays at level 5 and unevolved. 17 of its 21 moves carry an evolution card, across 6 distinct cards (Vigor, Sprint, Power, Reflexes, Armor and Synthesis). The strongest of them is Gust at 170.6 effective DPS, so that is the one worth holding a card for first.
Yveltal compared to similar partners
The two closest stat lines in the roster are Xerneas (+0 HP, +0 speed, same attack multiplier, +0 total) and Kyurem (-1 HP, -2 speed, same attack multiplier, -20 total). Against Xerneas, the two are level on speed and the two carry an identical ×1.42 attack multiplier, and the rank gap is 1 places. Those differences are what you actually trade when swapping partners, not a straight upgrade path, so neither side is a strict upgrade and the move pools have to break the tie.