What will you do if your manager always gives you difficult and nasty task, while he saves nice tasks for a colleague who is the boss's favorite?

patience and perseverance

Try to complete every task with patience. Your manager will surely understand the capabilities and qualities you possess and will consider your respectful attitude towards him. He will bring you to better role in his team for the sake of his own progress.

I will try my best to get a fair answer for this strange behavior, if get no reasonable answer then i will search hardly to find company with more comfort work environment  

It's time to find out about the real reason of it!But always look for a positive side - you'll gain a precious experience doing that, while other people probably are not able to do and half of it. Someday you'll win someone's respect

This is a very normal kind of situation which more or less all the employees has to face.

Such kind of situations does not last for a longer period of time and  has to be tackle very diplomatically..

The employee who are not performing well are automatically identified may not be immediately but in the due course of time and they are shown the way out of the company.

Even the managers having such kind of biased attitude also do not survive for a longer period of time. They either have to change the attitude or the organization as they are also answerable to his/her seniors.

However, if we take such situation on the ground of the personal growth, we are becoming more and more expert and experienced in handling such kind of situation which will add to our CV and also help in further assignments with different company

In terms of career growth, this kind of experience will help us in promotion, if not in the same company but may be else where.

Patience is the kew !

As you need the job you have to close one eye and wait for the better . 

• • Talk to this boss. Tell him what you need from him in term of direction, feedback and support. Be polite and focus on your needs. Telling the boss he’s a bad boss is counterproductive and won’t help you meet your goals.

• • Ask the manager how you can help him reach his goals. Make sure you listen well and provide the needed assistance.

• • Seek a mentor from among other managers or more skilled peers, with the full knowledge of your current manager, to enlarge your opportunity for experience.

• • If you’ve taken these actions, and they haven’t worked, go to your boss’s manager and ask for assistance. Or, you can go to your Human Resources staff first, to rehearse and gain advice. Understand that your current boss may never forgive you, so ensure you have done what you can do with him, before taking your issues up the line.

• • You may never hear what the boss’s boss or the HR staff did to help solve your bad manager’s behavior. It’s confidential. But, do allow some time to pass for the actions to have their desired impact.

• • If nothing changes, despite your best efforts, and you think the problem is that they don’t believe you, draw together coworkers who also experience the behavior. Visit the boss’s manager to help him see the size and impact of the behavior.

• • If you think the problem is that your boss can’t – or won’t – change, ask for a transfer to another department. This recommendation presumes you like your employer and your work.

• If a transfer or promotion is unavailable, begin your search for a new job. Fleeing is always an option. You may want to conduct your job search secretly, but under the circumstances, it may be time for you to go.

Thank you for your kind invitation Mr Ibrahim.

This is a very good question and often happens in reality yet cannot be dealt with properly. The second class treatment which one of the employees is getting can be classed as prejudice and discriminative because the manager favours another because of whatever reason. With respect to everyone who has said to stay patient I completely disagree, as part of the equality and diversity act everyone must be treated equally, opportunities must be delegated equally and the same would go with tasks. My advice in this situation would be to firstly really understand why a manager is acting that way, are they really favouriting another colleague? Are they giving you hard tasks to develop your skills? Can you carry out these tasks easily? How much training have you had on other tasks? How much knowledge do you have in other fields which your competition is in? Assess yourself, capabilities, talents and skills first before taking any action, if you have  however monitored the situation quietly for a while and believe that there is a form of favouritism then speak directly to the manager on a one-to-one, explain the effect it's having on you and your contribution to the business. If after a while it isn't resolved consult higher authorities in order to address the issue and put an end to it. No ONE should be mistreated or made to feel like they are less compared to another, this affects their character and confidence as well as have other affects which they may not display visually. Having a favourite employee is not wrong because there's always one or a few that excel further and make you proud, I myself have favourites however you have to be discreet and make sure your behaviour as a manager does not reflect your feelings.

Many of such things happen in companies but unfortunately there is not way to mitigate the effect as the boss attitude comes in different scenario, but one thing I would say that "Your boss trusts you a lot that you are talented, skillful to do a nasty hard task", the nice task and easy are for fools and dumb :). Respect your skills and love the tasks. One day such tasks will help you grow more. 

There are no difficult tasks for a professional! Especially if the given tasks are in the range of work description and duties ! Professionals accept  it without taking it personally, because if the personal moment is involved, no task can be accomplished properly.  

Face even the least favorable task with a smile because you have to consider every task as a learning curve, and not a personal issue with the one who assigned it. If you approach your position as a learning investment in your future, then you will have a better time focusing on the experience you gain as opposed to the person who assigned the "task". It becomes one of your "challenging" investments, and not a negative "task" assigned