Most of the eeveelutions. The stat values they all share just aren't built for a great 'mon. Basically the only way it's not going to have a glaring weakness in one of the defenses or worse, HP, is to lose all direct offensive capability.
Also, Ninetales. A fire type with limited bulk which is mostly on the special side when 2 of its weaknesses commonly use physical moves, and its best attacking stat is still low.
Gen 1: None. I was little and did not care for the pokemon's stats. Nowadays I wish Farfetch'd would have better stats.
Gen 2: Same as gen 2, but it's not as if stats mattered that much. I leveled a freaking Furret to Lv100 with no difficulty back then. Nowadays, I'm kinda sad for Granbull and Ursaring. Ursaring at least got nice abilities.
Gen3: Sableye and Mawile, I wanted to use either, but a try on Sableye put me off fast. So hard to train. Ludicolo didn't dissapoint tough. No CP yet.
Gen4: Luxray and Floatzel. After beating ingame with them and dabbling into CP for the first time, looking them up online disappointed me greatly. I didn't think about UU back then tough.
Gen5: Samurott felt stronger ingame than it actually was. Druddigon looks awesome but is pretty bad, sadly. I was happy to see Reuniclus strive tough.
Gen6: I'm very excited for Talonflame, Pangoro and Swirlix and really hope they'll be good. Pangoro being slow is already known, but I'm hoping for lots of power or bulk.
effective move breeding, Sceptile had issues fielding a fully special attacking set without move breeding iirc, so I wasn't optimizing my use of its stats using the ingame one.
he still does too, actually to many pokemon are this way. in game they end up limited options, there better choices come through post game breeding. torterra back in gen 4 was this way for me. and typhlosion is kinda this way too.
dandelion + flabebe + fairy wind = saddest moment in pokemon. 3ds fc. jd, 0602-6823-9646 or 0146.9112.0071