I think, from IND the biggest under achiever is Kapil Dev. He never played for his stats & hardly bothered for milestones. Kapil could have improved his Test batting average while one of crickets biggest loss is that Kapil (& his Captains) wasted him at 7, whereas he should have always played at 5. Apart from Kapil, I think I Pathan & UV had lot to offer in modern days, while an average of 35 & just 6 Test centuries don't reflect what an outstanding batsman Tiger Pataudi was (neither his Captaincy from the W/L ratio). UV could have ended with a Test career of 100+ matches; 6,000+ runs at 40+ (& SR of 75) & 200+ Test wickets at around 40. Unpopular statement, but those 2 Bombay guys were the over achievers - for that every second in Cricket field, they batted for own career.
For PAK (& probably in Cricket), the biggest underachiever was Imran Khan. Politics, WSC, injury, in-fights, groupings dented his career probably more than anyone - from 1983 to 1986 Imran lost 3 golden years & about 25 Tests when he was averaging <18 with ball & close to 50 with bat. Before that, lost 2-3 years to WSC in his mid 20s, & another 2-3 years at Oxford in his early 20s (though those 2-3 years made the Man Imran; playing for PIA or Habib Bank would have made him another Manzoor Elahi or Navid Anjum at best), yet he is arguably the greatest ever all-rounder. The other player from PAK I really felt missed out is Afridi - what a loser. He had a Test 100, a Test 50, a Test 5fer in his first 3 Tests & was good enough to finish with 400 Test wickets & 8,000 Test runs, both at around 35 (& a batting SR of 80+), in 20 years & 150+ Test career. He was once good enough to make the team as leg-spinner & had the capability to smash West Indian pacers for a 3 hours Century at Bridgetown - what a looser, I must say again. Apart from these 2, I think Wasim never focused on his batting & Inzi on his fitness - both of them should have significant better batting career. For LO version only, Malik is my biggest disappointment. He is easily the best middle-order of his generation behind MoYo & a quite effective spinner. There was a long thread on who is better ODI all-rounder MoHa or Malik & I still 'll go for Malik; that too after MoHa been the leading ODI all-rounder for best part of this decade - Malik was that good.
For SRL, I heard that Roy Dias was an outstanding stroke maker, but hardly achieved anything, but haven't seen him. Oblate, Malinga should have a much better Test career, but he focused too much on shorter version & struggled for fitness.
Current group of BD players are performing, but their predecessors didn't posses the mental toughness to sustain the pressure of International cricket, though some of them did have the ability. Two of them were Opi (Mehrab) & Rokon (Al Shahriar), talent wise probably at per or even better than Tamim, but never stood the pressure of International cricket & they were not dedicated enough. But the biggest loss for BD cricket is Ashraful - I watched him when he was 13-14 years old, practicing in South Dhaka clubs; he was as good as some of those averaging twice than him, but never fulfilled his potential.
AUS, ENG, SAF & NZ system is so good that, unless suffering from fitness; hardly any of their talented players misses out. Don't think Hick was underachiever - he was predominantly front foot player like Zaheer, brilliant against medium pacers (hence a County bully), until the West Indians made him smell the ball, everybody understood his medicine. Athers was a much, much better player than his average of 38, while Sir Ian Botham didn't do any justice to his God gifted ability. I think, had he not passed away at 23 for tuberculosis, Archie Jackson would have finished as the 2nd best batsman of his generation, behind the man he shared debut series, despite being born a year later (1909). I don't know what to believe, but for 2-3 years Bob Massie was the best swing bowler in world - before/after it's blank, don't know if he was under or over achiever. But among the Aussies I have seen, undoubtedly the biggest looser in Gary Gilmore - by the age of 25 he had 11 wickets in WC SF & Final, 58 Test wickets at 25, a batting average of 25+ with a century from 15 Tests ........ by 26 he was finished with his boozing & WSC. For the Kiwis, Martin Crow would have finished with 10+ Test runs had his keens not betrayed & for few years, Deon Nash was potentially worlds best all-rounder in making. Allot had a great WC, but don't think he was that good.
For SAF, the issue was different, so I won't rate Barry Richards or G Pollock as under achievers. In fact, opposite could be true as well - we have the picture of 24 years of Barry dominating Aussies of 27 years of GP at his prime, but we haven't seen them fail - 15 years of International cricket, who knows. Similar tale - had Viv Richards toured SAF with the rebel team of 1982, he would have finished with 5000+ Test runs at 65 (& a SR of 70+, in 70s!!!!!!), another 4000+ in ODI at 55 (& a SR close to 100 in 70s!!) & 2 World Cups under his belt. Oblate, may be Bret Schultz could have been better than Makhya, had he been fit enough, I don't know.
For WI, Lara & Richards were not underachievers actually - only a fool 'll measure them with the stats. I think, one player who really should feel disappointed looking 30 years back of his career is Carl Hooper. He finished with Test average of 36 & just about 100 Test wickets; was good enough to add at least 15 with his average & double, may be triple his wickets tally; and he was probably among top 10 slip catchers I have ever seen.
