tl;dr: In general no (but possible in special cases).
The answer to this question depends on the pension scheme (retirement plan) that applies to the employee. It may also depend on which part of the pension is based on contributions by the employee as opposed to the employer.
In general, the pension claim that an employee has is their property, and once earned ("accrued"), cannot be taken back - just as an employer cannot usually take back the wages they paid.
Strictly speaking, an employer could probably include a clause in their retirement plan that allows them to reduce the pension in case of firing, but this is very unusual, and would run afoul of some rules. For example, specifically, in the USA, to gain certain tax advantages (which are very desirable), a retirement plan must meet some minimum standards, and one of them is that the "accrued benefit" must be "noforfeitable". For example:
(a) General rule - A trust shall not constitute a qualified trust
under section 401(a) unless the plan of which such trust is a part
provides that an employee’s right to his normal retirement benefit is
nonforfeitable upon the attainment of normal retirement age (as
defined in paragraph (8)) and in addition satisfies [...]
(1) Employee contributions
A plan satisfies the requirements of this paragraph if an employee’s
rights in his accrued benefit derived from his own contributions are
26 U.S. Code § 411 - Minimum vesting standards
So generally, once you earned your pension, it's yours.
In the USA, most of this is regulated in the Employee Retirement Income Security Act of 1974 (ERISA), including the rules about forfeiture of contributions. Thanks to ohwilleke for mentioning this.
One notable exception is the public sector (which the question did not ask about): In many US states public sector employees or politicians forfeit their pension if they commit a felony relating to official duties. There is no such rule for pensions in the private sector, neither in the USA nor in most other countries I know of.
See e.g. State Pension Forfeiture Laws for an overview.