Watchin Gintama... as far as comedy and parody animes are concerned, this is the best by far.. creative and stupid in a way thats not for kids but for adults... excellent!!
Thats a very unfair attack on bleach... cause onepiece is just the same. during the cp9 arc they met openents who are stronger than them and suddenly in a short inexplicable amount of time they got stronger and beat them... so ya they also 'cut corners' as you put it!! And mind you ichigo has always been training since the beginning, thats hows he always gets stronger. Atleast bleach they show us part of the training unlike one piece.
Probably renji..... and as far as renji and ikkaku are concerned......if u remeber when ichigo first came to soul society, he beat ikkaku quite easily but had more trouble wit renji. and they both used shikai to fight him.