>>16438899252 Atk Infernape Close Combat vs. 252 HP / 0 Def Shuckle: 81-96 (33.1 - 39.3%)
252 Atk Infernape Close Combat vs. 128 HP / 64 Def Shuckle: 78-93 (36.6 - 43.6%)
252 Atk Infernape Close Combat vs. 0 HP / 128 Def Shuckle: 76-90 (41.9 - 49.7%)
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252 Atk Infernape Close Combat vs. 252 HP / 0 Def Blissey: 1410-1662 (197.4 - 232.7%)
252 Atk Infernape Close Combat vs. 128 HP / 64 Def Blissey: 1098-1292 (160.7 - 189.1%)
252 Atk Infernape Close Combat vs. 0 HP / 128 Def Blissey: 900-1058 (138.2 - 162.5%)
HP/Defense RATIOS are far more important.
Also:
252 Atk Infernape Flare Blitz vs. 252 HP / 252 Def Shuckle: 72-85 (29.5 - 34.8%)
252 Atk Infernape Flare Blitz vs. 252 HP / 252 Def Blissey: 333-393 (46.6 - 55%)
Looks like shuckle takes the advantage in this category due to the fact that HP has a high static addition (The lowest a pokemon's HP can be at 100 when it's calculated with the formula would be 120, with a base 5 HP and no IVs.)