I couldn't agree with you more Mishra. There are so many ways to beat Chansey it's not even funny. Most physical attacker can deal substantial damage to it with STAB moves or SE moves (let's face it, a good number of physical attackers carry fighting moves). In fact, it is set up bait for a ton of threats that take advantage of Chansey's weak power, like Ursaring, Snorlax, Kingdra, and NPdoom (yes, at +6 Fire Blast does a shitload of damage). So physical attackers beat it and set up sweepers beat it. Most offensive and balanced teams have at least one of those. Furthermore, stall beats chansey extremely well. Toxic shuts it down, and all that's needed is a few protects or a ghost type (for seismic toss immunity) to wear it down completely. Leech Seed completely stops it, as each turn you recover about 40 HP, on top of leftovers healing (40 HP is for 4 HP variants. 252 HP variants heal 44 HP per turn). Any kind of item changing such as knock off or trick makes it totally useless. And Taunt + Recovery is absolutely awful for it.
If you are having Chansey troubles, why not try a Crobat. Strong, physical Brave Bird STAB, Super Fang, immunity to Toxic, and Taunt.
Or just any fighting type.
Or any physical attacker. Literally. Shit even Ambipom can cleanly 2HKO with Return or Low Sweep. Snorlax sets up all over Chansey's face, and really takes little damage from Seismic Toss due to its high HP.
A lot of people don't like Chansey, because it forces out their special attackers, but that's just how things are. Chansey may be annoying but is by no means ban worthy.